Update to PHPMailer 6.6.0 with composer (#4329)

* Install PHPMailer 6.5.1 with composer

* Fix folder name for phpmailer

* Update PHPMailer to v6.6.0, add LICENSE and README.md

* remove composer and autoload.php after install/update

* Fix path to PHPMailer for PHPStan

* Remove lib/composer.lock, lock PHPMailer at version 6.6.0

* Improve PSR-4 autoloading for PHPMailer

* Markdownlint ignore

* Delete some obvious comments

* ignores

* Support composer update --no-autoloader

* Automatic cleaning
With rules based on https://github.com/PHPMailer/PHPMailer/blob/master/README.md#minimal-installation

* Readme gitignore hint

Co-authored-by: Alexandre Alapetite <alexandre@alapetite.fr>

15 files changed, 863 insertions, 33 deletions

diff --git a/.markdownlintignore b/.markdownlintignore
index 4036833d2..b31ea81ba 100644
--- a/.markdownlintignore
+++ b/.markdownlintignore
@@ -1,4 +1,5 @@
 lib/CssXPath/
+lib/phpmailer/
 node_modules/
 p/scripts/vendor/
 vendor/
diff --git a/.typos.toml b/.typos.toml
index afc91c284..b05117ccf 100644
--- a/.typos.toml
+++ b/.typos.toml
@@ -30,7 +30,7 @@ extend-exclude = [
 	"data/",
 	"docs/fr/",
 	"lib/CssXPath/",
-	"lib/PHPMailer",
+	"lib/phpmailer/",
 	"lib/SimplePie/",
 	"node_modules/",
 	"p/scripts/vendor/",
diff --git a/lib/.gitignore b/lib/.gitignore
new file mode 100644
index 000000000..f1e6fdd7e
--- /dev/null
+++ b/lib/.gitignore
@@ -0,0 +1,10 @@
+autoload.php
+composer.lock
+composer/
+phpmailer/phpmailer/*oauth*
+phpmailer/phpmailer/COMMITMENT*
+phpmailer/phpmailer/composer.*
+phpmailer/phpmailer/language/
+phpmailer/phpmailer/SECURITY*
+phpmailer/phpmailer/src/OAuth*
+phpmailer/phpmailer/src/POP3.php
diff --git a/lib/README.md b/lib/README.md
new file mode 100644
index 000000000..a7cbd97e6
--- /dev/null
+++ b/lib/README.md
@@ -0,0 +1,12 @@
+# Libraries
+
+## Updating libraries
+
+Some of the libraries in this folder can be updated semi-automatically by invoking:
+
+```sh
+cd ./FreshRSS/lib/
+composer update --no-autoloader
+```
+
+Remember to read the change-logs, proof-read the changes, preserve possible local patches, add irrelevant files to [`.gitignore`](.gitignore) (minimal installation), and test before committing.
diff --git a/lib/composer.json b/lib/composer.json
new file mode 100644
index 000000000..3d307f6e8
--- /dev/null
+++ b/lib/composer.json
@@ -0,0 +1,17 @@
+{
+    "name": "freshrss.org/freshrss",
+    "description": "A free, self-hostable aggregator",
+    "type": "project",
+    "homepage": "https://freshrss.org/",
+    "license": "AGPL-3.0",
+    "require": {
+        "php": ">=7.0.0",
+        "phpmailer/phpmailer": "6.6.0"
+    },
+    "config": {
+        "vendor-dir": "./"
+    },
+    "scripts": {
+        "post-update-cmd": "git clean -d -f -X ."
+    }
+}
diff --git a/lib/lib_rss.php b/lib/lib_rss.php
index ad7d9f523..a4a9df36a 100644
--- a/lib/lib_rss.php
+++ b/lib/lib_rss.php
@@ -9,6 +9,13 @@ if (!function_exists('mb_strcut')) {
 	}
 }
 
+if (!function_exists('str_starts_with')) {
+	/** Polyfill for PHP <8.0 */
+	function str_starts_with(string $haystack, string $needle): bool {
+		return strncmp($haystack, $needle, strlen($needle)) === 0;
+	}
+}
+
 // @phpstan-ignore-next-line
 if (COPY_SYSLOG_TO_STDERR) {
 	openlog('FreshRSS', LOG_CONS | LOG_ODELAY | LOG_PID | LOG_PERROR, LOG_USER);
@@ -47,8 +54,11 @@ function classAutoloader($class) {
 		include(LIB_PATH . '/SimplePie/' . str_replace('_', '/', $class) . '.php');
 	} elseif (strpos($class, 'CssXPath') !== false) {
 		include(LIB_PATH . '/CssXPath/' . basename(str_replace('\\', '/', $class)) . '.php');
-	} elseif (strpos($class, 'PHPMailer') === 0) {
-		include(LIB_PATH . '/' . str_replace('\\', '/', $class) . '.php');
+	} elseif (str_starts_with($class, 'PHPMailer\\PHPMailer\\')) {
+		$prefix = 'PHPMailer\\PHPMailer\\';
+		$base_dir = LIB_PATH . '/phpmailer/phpmailer/src/';
+		$relative_class_name = substr($class, strlen($prefix));
+		require $base_dir . str_replace('\\', '/', $relative_class_name) . '.php';
 	}
 }
 
diff --git a/lib/phpmailer/phpmailer/LICENSE b/lib/phpmailer/phpmailer/LICENSE
new file mode 100644
index 000000000..f166cc57b
--- /dev/null
+++ b/lib/phpmailer/phpmailer/LICENSE
@@ -0,0 +1,502 @@
+                  GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 2.1, February 1999
+
+ Copyright (C) 1991, 1999 Free Software Foundation, Inc.
+ 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ Everyone is permitted to copy and distribute verbatim copies
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+[This is the first released version of the Lesser GPL.  It also counts
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+                     END OF TERMS AND CONDITIONS
+
+           How to Apply These Terms to Your New Libraries
+
+  If you develop a new library, and you want it to be of the greatest
+possible use to the public, we recommend making it free software that
+everyone can redistribute and change.  You can do so by permitting
+redistribution under these terms (or, alternatively, under the terms of the
+ordinary General Public License).
+
+  To apply these terms, attach the following notices to the library.  It is
+safest to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least the
+"copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the library's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+Also add information on how to contact you by electronic and paper mail.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the library, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the
+  library `Frob' (a library for tweaking knobs) written by James Random Hacker.
+
+  <signature of Ty Coon>, 1 April 1990
+  Ty Coon, President of Vice
+
+That's all there is to it!
\ No newline at end of file
diff --git a/lib/phpmailer/phpmailer/README.md b/lib/phpmailer/phpmailer/README.md
new file mode 100644
index 000000000..81b089763
--- /dev/null
+++ b/lib/phpmailer/phpmailer/README.md
@@ -0,0 +1,227 @@
+![PHPMailer](https://raw.github.com/PHPMailer/PHPMailer/master/examples/images/phpmailer.png)
+
+# PHPMailer – A full-featured email creation and transfer class for PHP
+
+[![Test status](https://github.com/PHPMailer/PHPMailer/workflows/Tests/badge.svg)](https://github.com/PHPMailer/PHPMailer/actions)
+[![codecov.io](https://codecov.io/gh/PHPMailer/PHPMailer/branch/master/graph/badge.svg?token=iORZpwmYmM)](https://codecov.io/gh/PHPMailer/PHPMailer)
+[![Latest Stable Version](https://poser.pugx.org/phpmailer/phpmailer/v/stable.svg)](https://packagist.org/packages/phpmailer/phpmailer)
+[![Total Downloads](https://poser.pugx.org/phpmailer/phpmailer/downloads)](https://packagist.org/packages/phpmailer/phpmailer)
+[![License](https://poser.pugx.org/phpmailer/phpmailer/license.svg)](https://packagist.org/packages/phpmailer/phpmailer)
+[![API Docs](https://github.com/phpmailer/phpmailer/workflows/Docs/badge.svg)](https://phpmailer.github.io/PHPMailer/)
+
+## Features
+- Probably the world's most popular code for sending email from PHP!
+- Used by many open-source projects: WordPress, Drupal, 1CRM, SugarCRM, Yii, Joomla! and many more
+- Integrated SMTP support – send without a local mail server
+- Send emails with multiple To, CC, BCC and Reply-to addresses
+- Multipart/alternative emails for mail clients that do not read HTML email
+- Add attachments, including inline
+- Support for UTF-8 content and 8bit, base64, binary, and quoted-printable encodings
+- SMTP authentication with LOGIN, PLAIN, CRAM-MD5, and XOAUTH2 mechanisms over SMTPS and SMTP+STARTTLS transports
+- Validates email addresses automatically
+- Protects against header injection attacks
+- Error messages in over 50 languages!
+- DKIM and S/MIME signing support
+- Compatible with PHP 5.5 and later, including PHP 8.1
+- Namespaced to prevent name clashes
+- Much more!
+
+## Why you might need it
+Many PHP developers need to send email from their code. The only PHP function that supports this directly is [`mail()`](https://www.php.net/manual/en/function.mail.php). However, it does not provide any assistance for making use of popular features such as encryption, authentication, HTML messages, and attachments.
+
+Formatting email correctly is surprisingly difficult. There are myriad overlapping (and conflicting) standards, requiring tight adherence to horribly complicated formatting and encoding rules – the vast majority of code that you'll find online that uses the `mail()` function directly is just plain wrong, if not unsafe!
+
+The PHP `mail()` function usually sends via a local mail server, typically fronted by a `sendmail` binary on Linux, BSD, and macOS platforms, however, Windows usually doesn't include a local mail server; PHPMailer's integrated SMTP client allows email sending on all platforms without needing a local mail server. Be aware though, that the `mail()` function should be avoided when possible; it's both faster and [safer](https://exploitbox.io/paper/Pwning-PHP-Mail-Function-For-Fun-And-RCE.html) to use SMTP to localhost.
+
+*Please* don't be tempted to do it yourself – if you don't use PHPMailer, there are many other excellent libraries that
+you should look at before rolling your own. Try [SwiftMailer](https://swiftmailer.symfony.com/)
+, [Laminas/Mail](https://docs.laminas.dev/laminas-mail/), [ZetaComponents](https://github.com/zetacomponents/Mail) etc.
+
+## License
+This software is distributed under the [LGPL 2.1](http://www.gnu.org/licenses/lgpl-2.1.html) license, along with the [GPL Cooperation Commitment](https://gplcc.github.io/gplcc/). Please read [LICENSE](https://github.com/PHPMailer/PHPMailer/blob/master/LICENSE) for information on the software availability and distribution.
+
+## Installation & loading
+PHPMailer is available on [Packagist](https://packagist.org/packages/phpmailer/phpmailer) (using semantic versioning), and installation via [Composer](https://getcomposer.org) is the recommended way to install PHPMailer. Just add this line to your `composer.json` file:
+
+```json
+"phpmailer/phpmailer": "^6.5"
+```
+
+or run
+
+```sh
+composer require phpmailer/phpmailer
+```
+
+Note that the `vendor` folder and the `vendor/autoload.php` script are generated by Composer; they are not part of PHPMailer.
+
+If you want to use the Gmail XOAUTH2 authentication class, you will also need to add a dependency on the `league/oauth2-client` package in your `composer.json`.
+
+Alternatively, if you're not using Composer, you
+can [download PHPMailer as a zip file](https://github.com/PHPMailer/PHPMailer/archive/master.zip), (note that docs and examples are not included in the zip file), then copy the contents of the PHPMailer folder into one of the `include_path` directories specified in your PHP configuration and load each class file manually:
+
+```php
+<?php
+use PHPMailer\PHPMailer\PHPMailer;
+use PHPMailer\PHPMailer\Exception;
+
+require 'path/to/PHPMailer/src/Exception.php';
+require 'path/to/PHPMailer/src/PHPMailer.php';
+require 'path/to/PHPMailer/src/SMTP.php';
+```
+
+If you're not using the `SMTP` class explicitly (you're probably not), you don't need a `use` line for the SMTP class. Even if you're not using exceptions, you do still need to load the `Exception` class as it is used internally.
+
+## Legacy versions
+PHPMailer 5.2 (which is compatible with PHP 5.0 — 7.0) is no longer supported, even for security updates. You will find the latest version of 5.2 in the [5.2-stable branch](https://github.com/PHPMailer/PHPMailer/tree/5.2-stable). If you're using PHP 5.5 or later (which you should be), switch to the 6.x releases.
+
+### Upgrading from 5.2
+The biggest changes are that source files are now in the `src/` folder, and PHPMailer now declares the namespace `PHPMailer\PHPMailer`. This has several important effects – [read the upgrade guide](https://github.com/PHPMailer/PHPMailer/tree/master/UPGRADING.md) for more details.
+
+### Minimal installation
+While installing the entire package manually or with Composer is simple, convenient, and reliable, you may want to include only vital files in your project. At the very least you will need [src/PHPMailer.php](https://github.com/PHPMailer/PHPMailer/tree/master/src/PHPMailer.php). If you're using SMTP, you'll need [src/SMTP.php](https://github.com/PHPMailer/PHPMailer/tree/master/src/SMTP.php), and if you're using POP-before SMTP (*very* unlikely!), you'll need [src/POP3.php](https://github.com/PHPMailer/PHPMailer/tree/master/src/POP3.php). You can skip the [language](https://github.com/PHPMailer/PHPMailer/tree/master/language/) folder if you're not showing errors to users and can make do with English-only errors. If you're using XOAUTH2 you will need [src/OAuth.php](https://github.com/PHPMailer/PHPMailer/tree/master/src/OAuth.php) as well as the Composer dependencies for the services you wish to authenticate with. Really, it's much easier to use Composer!
+
+## A Simple Example
+
+```php
+<?php
+//Import PHPMailer classes into the global namespace
+//These must be at the top of your script, not inside a function
+use PHPMailer\PHPMailer\PHPMailer;
+use PHPMailer\PHPMailer\SMTP;
+use PHPMailer\PHPMailer\Exception;
+
+//Load Composer's autoloader
+require 'vendor/autoload.php';
+
+//Create an instance; passing `true` enables exceptions
+$mail = new PHPMailer(true);
+
+try {
+    //Server settings
+    $mail->SMTPDebug = SMTP::DEBUG_SERVER;                      //Enable verbose debug output
+    $mail->isSMTP();                                            //Send using SMTP
+    $mail->Host       = 'smtp.example.com';                     //Set the SMTP server to send through
+    $mail->SMTPAuth   = true;                                   //Enable SMTP authentication
+    $mail->Username   = 'user@example.com';                     //SMTP username
+    $mail->Password   = 'secret';                               //SMTP password
+    $mail->SMTPSecure = PHPMailer::ENCRYPTION_SMTPS;            //Enable implicit TLS encryption
+    $mail->Port       = 465;                                    //TCP port to connect to; use 587 if you have set `SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS`
+
+    //Recipients
+    $mail->setFrom('from@example.com', 'Mailer');
+    $mail->addAddress('joe@example.net', 'Joe User');     //Add a recipient
+    $mail->addAddress('ellen@example.com');               //Name is optional
+    $mail->addReplyTo('info@example.com', 'Information');
+    $mail->addCC('cc@example.com');
+    $mail->addBCC('bcc@example.com');
+
+    //Attachments
+    $mail->addAttachment('/var/tmp/file.tar.gz');         //Add attachments
+    $mail->addAttachment('/tmp/image.jpg', 'new.jpg');    //Optional name
+
+    //Content
+    $mail->isHTML(true);                                  //Set email format to HTML
+    $mail->Subject = 'Here is the subject';
+    $mail->Body    = 'This is the HTML message body <b>in bold!</b>';
+    $mail->AltBody = 'This is the body in plain text for non-HTML mail clients';
+
+    $mail->send();
+    echo 'Message has been sent';
+} catch (Exception $e) {
+    echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
+}
+```
+
+You'll find plenty to play with in the [examples](https://github.com/PHPMailer/PHPMailer/tree/master/examples) folder, which covers many common scenarios including sending through gmail, building contact forms, sending to mailing lists, and more.
+
+If you are re-using the instance (e.g. when sending to a mailing list), you may need to clear the recipient list to avoid sending duplicate messages. See [the mailing list example](https://github.com/PHPMailer/PHPMailer/blob/master/examples/mailing_list.phps) for further guidance.
+
+That's it. You should now be ready to use PHPMailer!
+
+## Localization
+PHPMailer defaults to English, but in the [language](https://github.com/PHPMailer/PHPMailer/tree/master/language/) folder you'll find many translations for PHPMailer error messages that you may encounter. Their filenames contain [ISO 639-1](http://en.wikipedia.org/wiki/ISO_639-1) language code for the translations, for example `fr` for French. To specify a language, you need to tell PHPMailer which one to use, like this:
+
+```php
+//To load the French version
+$mail->setLanguage('fr', '/optional/path/to/language/directory/');
+```
+
+We welcome corrections and new languages – if you're looking for corrections, run the [PHPMailerLangTest.php](https://github.com/PHPMailer/PHPMailer/tree/master/test/PHPMailerLangTest.php) script in the tests folder and it will show any missing translations.
+
+## Documentation
+Start reading at the [GitHub wiki](https://github.com/PHPMailer/PHPMailer/wiki). If you're having trouble, head for [the troubleshooting guide](https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting) as it's frequently updated.
+
+Examples of how to use PHPMailer for common scenarios can be found in the [examples](https://github.com/PHPMailer/PHPMailer/tree/master/examples) folder. If you're looking for a good starting point, we recommend you start with [the Gmail example](https://github.com/PHPMailer/PHPMailer/tree/master/examples/gmail.phps).
+
+To reduce PHPMailer's deployed code footprint, examples are not included if you load PHPMailer via Composer or via [GitHub's zip file download](https://github.com/PHPMailer/PHPMailer/archive/master.zip), so you'll need to either clone the git repository or use the above links to get to the examples directly.
+
+Complete generated API documentation is [available online](https://phpmailer.github.io/PHPMailer/).
+
+You can generate complete API-level documentation by running `phpdoc` in the top-level folder, and documentation will appear in the `docs` folder, though you'll need to have [PHPDocumentor](http://www.phpdoc.org) installed. You may find [the unit tests](https://github.com/PHPMailer/PHPMailer/blob/master/test/PHPMailerTest.php) a good reference for how to do various operations such as encryption.
+
+If the documentation doesn't cover what you need, search the [many questions on Stack Overflow](http://stackoverflow.com/questions/tagged/phpmailer), and before you ask a question about "SMTP Error: Could not connect to SMTP host.", [read the troubleshooting guide](https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting).
+
+## Tests
+[PHPMailer tests](https://github.com/PHPMailer/PHPMailer/tree/master/test/) use PHPUnit 9, with [a polyfill](https://github.com/Yoast/PHPUnit-Polyfills) to let 9-style tests run on older PHPUnit and PHP versions.
+
+[![Test status](https://github.com/PHPMailer/PHPMailer/workflows/Tests/badge.svg)](https://github.com/PHPMailer/PHPMailer/actions)
+
+If this isn't passing, is there something you can do to help?
+
+## Security
+Please disclose any vulnerabilities found responsibly – report security issues to the maintainers privately.
+
+See [SECURITY](https://github.com/PHPMailer/PHPMailer/tree/master/SECURITY.md) and [PHPMailer's security advisories on GitHub](https://github.com/PHPMailer/PHPMailer/security). 
+
+## Contributing
+Please submit bug reports, suggestions and pull requests to the [GitHub issue tracker](https://github.com/PHPMailer/PHPMailer/issues).
+
+We're particularly interested in fixing edge-cases, expanding test coverage and updating translations.
+
+If you found a mistake in the docs, or want to add something, go ahead and amend the wiki – anyone can edit it.
+
+If you have git clones from prior to the move to the PHPMailer GitHub organisation, you'll need to update any remote URLs referencing the old GitHub location with a command like this from within your clone:
+
+```sh
+git remote set-url upstream https://github.com/PHPMailer/PHPMailer.git
+```
+
+Please *don't* use the SourceForge or Google Code projects any more; they are obsolete and no longer maintained.
+
+## Sponsorship
+Development time and resources for PHPMailer are provided by [Smartmessages.net](https://info.smartmessages.net/), the world's only privacy-first email marketing system.
+
+<a href="https://info.smartmessages.net/"><img src="https://www.smartmessages.net/img/smartmessages-logo.svg" width="550" alt="Smartmessages.net privacy-first email marketing logo"></a>
+
+Donations are very welcome, whether in beer 🍺, T-shirts 👕, or cold, hard cash 💰. Sponsorship through GitHub is a simple and convenient way to say "thank you" to PHPMailer's maintainers and contributors – just click the "Sponsor" button [on the project page](https://github.com/PHPMailer/PHPMailer). If your company uses PHPMailer, consider taking part in Tidelift's enterprise support programme.
+
+## PHPMailer For Enterprise
+
+Available as part of the Tidelift Subscription.
+
+The maintainers of PHPMailer and thousands of other packages are working with Tidelift to deliver commercial
+support and maintenance for the open source packages you use to build your applications. Save time, reduce risk, and
+improve code health, while paying the maintainers of the exact packages you
+use. [Learn more.](https://tidelift.com/subscription/pkg/packagist-phpmailer-phpmailer?utm_source=packagist-phpmailer-phpmailer&utm_medium=referral&utm_campaign=enterprise&utm_term=repo)
+
+## Changelog
+See [changelog](changelog.md).
+
+## History
+- PHPMailer was originally written in 2001 by Brent R. Matzelle as a [SourceForge project](http://sourceforge.net/projects/phpmailer/).
+- [Marcus Bointon](https://github.com/Synchro) (`coolbru` on SF) and Andy Prevost (`codeworxtech`) took over the project in 2004.
+- Became an Apache incubator project on Google Code in 2010, managed by Jim Jagielski.
+- Marcus created [his fork on GitHub](https://github.com/Synchro/PHPMailer) in 2008.
+- Jim and Marcus decide to join forces and use GitHub as the canonical and official repo for PHPMailer in 2013.
+- PHPMailer moves to [the PHPMailer organisation](https://github.com/PHPMailer) on GitHub in 2013.
+
+### What's changed since moving from SourceForge?
+- Official successor to the SourceForge and Google Code projects.
+- Test suite.
+- Continuous integration with Github Actions.
+- Composer support.
+- Public development.
+- Additional languages and language strings.
+- CRAM-MD5 authentication support.
+- Preserves full repo history of authors, commits and branches from the original SourceForge project.
diff --git a/lib/phpmailer/phpmailer/VERSION b/lib/phpmailer/phpmailer/VERSION
new file mode 100644
index 000000000..cd802a1ec
--- /dev/null
+++ b/lib/phpmailer/phpmailer/VERSION
@@ -0,0 +1 @@
+6.6.0
\ No newline at end of file
diff --git a/lib/PHPMailer/PHPMailer/Exception.php b/lib/phpmailer/phpmailer/src/Exception.php
index 52eaf9515..52eaf9515 100644
--- a/lib/PHPMailer/PHPMailer/Exception.php
+++ b/lib/phpmailer/phpmailer/src/Exception.php
diff --git a/lib/PHPMailer/PHPMailer/PHPMailer.php b/lib/phpmailer/phpmailer/src/PHPMailer.php
index 5b6dcfad6..718216b54 100644
--- a/lib/PHPMailer/PHPMailer/PHPMailer.php
+++ b/lib/phpmailer/phpmailer/src/PHPMailer.php
@@ -358,9 +358,9 @@ class PHPMailer
     public $AuthType = '';
 
     /**
-     * An instance of the PHPMailer OAuth class.
+     * An implementation of the PHPMailer OAuthTokenProvider interface.
      *
-     * @var OAuth
+     * @var OAuthTokenProvider
      */
     protected $oauth;
 
@@ -750,7 +750,7 @@ class PHPMailer
      *
      * @var string
      */
-    const VERSION = '6.5.1';
+    const VERSION = '6.6.0';
 
     /**
      * Error severity: message only, continue processing.
@@ -1185,6 +1185,7 @@ class PHPMailer
      *
      * @param string $addrstr The address list string
      * @param bool   $useimap Whether to use the IMAP extension to parse the list
+     * @param string $charset The charset to use when decoding the address list string.
      *
      * @return array
      */
@@ -1451,7 +1452,12 @@ class PHPMailer
                 $errorcode = 0;
                 if (defined('INTL_IDNA_VARIANT_UTS46')) {
                     //Use the current punycode standard (appeared in PHP 7.2)
-                    $punycode = idn_to_ascii($domain, $errorcode, \INTL_IDNA_VARIANT_UTS46);
+                    $punycode = idn_to_ascii(
+                        $domain,
+                        \IDNA_DEFAULT | \IDNA_USE_STD3_RULES | \IDNA_CHECK_BIDI |
+                            \IDNA_CHECK_CONTEXTJ | \IDNA_NONTRANSITIONAL_TO_ASCII,
+                        \INTL_IDNA_VARIANT_UTS46
+                    );
                 } elseif (defined('INTL_IDNA_VARIANT_2003')) {
                     //Fall back to this old, deprecated/removed encoding
                     $punycode = idn_to_ascii($domain, $errorcode, \INTL_IDNA_VARIANT_2003);
@@ -1697,7 +1703,10 @@ class PHPMailer
         //Sendmail docs: http://www.sendmail.org/~ca/email/man/sendmail.html
         //Qmail docs: http://www.qmail.org/man/man8/qmail-inject.html
         //Example problem: https://www.drupal.org/node/1057954
-        if (empty($this->Sender) && !empty(ini_get('sendmail_from'))) {
+
+        //PHP 5.6 workaround
+        $sendmail_from_value = ini_get('sendmail_from');
+        if (empty($this->Sender) && !empty($sendmail_from_value)) {
             //PHP config has a sender address we can use
             $this->Sender = ini_get('sendmail_from');
         }
@@ -1734,7 +1743,7 @@ class PHPMailer
                 fwrite($mail, $header);
                 fwrite($mail, $body);
                 $result = pclose($mail);
-                $addrinfo = static::parseAddresses($toAddr, true, $this->charSet);
+                $addrinfo = static::parseAddresses($toAddr, true, $this->CharSet);
                 $this->doCallback(
                     ($result === 0),
                     [[$addrinfo['address'], $addrinfo['name']]],
@@ -1789,7 +1798,13 @@ class PHPMailer
      */
     protected static function isShellSafe($string)
     {
-        //Future-proof
+        //It's not possible to use shell commands safely (which includes the mail() function) without escapeshellarg,
+        //but some hosting providers disable it, creating a security problem that we don't want to have to deal with,
+        //so we don't.
+        if (!function_exists('escapeshellarg') || !function_exists('escapeshellcmd')) {
+            return false;
+        }
+
         if (
             escapeshellcmd($string) !== $string
             || !in_array(escapeshellarg($string), ["'$string'", "\"$string\""])
@@ -1879,7 +1894,10 @@ class PHPMailer
         //Qmail docs: http://www.qmail.org/man/man8/qmail-inject.html
         //Example problem: https://www.drupal.org/node/1057954
         //CVE-2016-10033, CVE-2016-10045: Don't pass -f if characters will be escaped.
-        if (empty($this->Sender) && !empty(ini_get('sendmail_from'))) {
+
+        //PHP 5.6 workaround
+        $sendmail_from_value = ini_get('sendmail_from');
+        if (empty($this->Sender) && !empty($sendmail_from_value)) {
             //PHP config has a sender address we can use
             $this->Sender = ini_get('sendmail_from');
         }
@@ -1894,7 +1912,7 @@ class PHPMailer
         if ($this->SingleTo && count($toArr) > 1) {
             foreach ($toArr as $toAddr) {
                 $result = $this->mailPassthru($toAddr, $this->Subject, $body, $header, $params);
-                $addrinfo = static::parseAddresses($toAddr, true, $this->charSet);
+                $addrinfo = static::parseAddresses($toAddr, true, $this->CharSet);
                 $this->doCallback(
                     $result,
                     [[$addrinfo['address'], $addrinfo['name']]],
@@ -2143,7 +2161,8 @@ class PHPMailer
                     }
                     if ($tls) {
                         if (!$this->smtp->startTLS()) {
-                            throw new Exception($this->lang('connect_host'));
+                            $message = $this->getSmtpErrorMessage('connect_host');
+                            throw new Exception($message);
                         }
                         //We must resend EHLO after TLS negotiation
                         $this->smtp->hello($hello);
@@ -2173,6 +2192,10 @@ class PHPMailer
         //As we've caught all exceptions, just report whatever the last one was
         if ($this->exceptions && null !== $lastexception) {
             throw $lastexception;
+        } elseif ($this->exceptions) {
+            // no exception was thrown, likely $this->smtp->connect() failed
+            $message = $this->getSmtpErrorMessage('connect_host');
+            throw new Exception($message);
         }
 
         return false;
@@ -2196,7 +2219,7 @@ class PHPMailer
      * @param string $langcode  ISO 639-1 2-character language code (e.g. French is "fr")
      *                          Optionally, the language code can be enhanced with a 4-character
      *                          script annotation and/or a 2-character country annotation.
-     * @param string $lang_path Path to the language file directory, with trailing separator (slash).D
+     * @param string $lang_path Path to the language file directory, with trailing separator (slash)
      *                          Do not set this from user input!
      *
      * @return bool Returns true if the requested language was loaded, false otherwise.
@@ -2619,16 +2642,15 @@ class PHPMailer
             $result .= $this->headerLine('X-Priority', $this->Priority);
         }
         if ('' === $this->XMailer) {
+            //Empty string for default X-Mailer header
             $result .= $this->headerLine(
                 'X-Mailer',
                 'PHPMailer ' . self::VERSION . ' (https://github.com/PHPMailer/PHPMailer)'
             );
-        } else {
-            $myXmailer = trim($this->XMailer);
-            if ($myXmailer) {
-                $result .= $this->headerLine('X-Mailer', $myXmailer);
-            }
-        }
+        } elseif (is_string($this->XMailer) && trim($this->XMailer) !== '') {
+            //Some string
+            $result .= $this->headerLine('X-Mailer', trim($this->XMailer));
+        } //Other values result in no X-Mailer header
 
         if ('' !== $this->ConfirmReadingTo) {
             $result .= $this->headerLine('Disposition-Notification-To', '<' . $this->ConfirmReadingTo . '>');
@@ -4111,6 +4133,26 @@ class PHPMailer
     }
 
     /**
+     * Build an error message starting with a generic one and adding details if possible.
+     *
+     * @param string $base_key
+     * @return string
+     */
+    private function getSmtpErrorMessage($base_key)
+    {
+        $message = $this->lang($base_key);
+        $error = $this->smtp->getError();
+        if (!empty($error['error'])) {
+            $message .= ' ' . $error['error'];
+            if (!empty($error['detail'])) {
+                $message .= ' ' . $error['detail'];
+            }
+        }
+
+        return $message;
+    }
+
+    /**
      * Check if an error occurred.
      *
      * @return bool True if an error did occur
@@ -5010,9 +5052,9 @@ class PHPMailer
     }
 
     /**
-     * Get the OAuth instance.
+     * Get the OAuthTokenProvider instance.
      *
-     * @return OAuth
+     * @return OAuthTokenProvider
      */
     public function getOAuth()
     {
@@ -5020,9 +5062,9 @@ class PHPMailer
     }
 
     /**
-     * Set an OAuth instance.
+     * Set an OAuthTokenProvider instance.
      */
-    public function setOAuth(OAuth $oauth)
+    public function setOAuth(OAuthTokenProvider $oauth)
     {
         $this->oauth = $oauth;
     }
diff --git a/lib/PHPMailer/PHPMailer/SMTP.php b/lib/phpmailer/phpmailer/src/SMTP.php
index 565441e6b..5ecad21da 100644
--- a/lib/PHPMailer/PHPMailer/SMTP.php
+++ b/lib/phpmailer/phpmailer/src/SMTP.php
@@ -35,7 +35,7 @@ class SMTP
      *
      * @var string
      */
-    const VERSION = '6.5.1';
+    const VERSION = '6.6.0';
 
     /**
      * SMTP line break constant.
@@ -187,6 +187,7 @@ class SMTP
         'SendGrid' => '/[\d]{3} Ok: queued as (.*)/',
         'CampaignMonitor' => '/[\d]{3} 2.0.0 OK:([a-zA-Z\d]{48})/',
         'Haraka' => '/[\d]{3} Message Queued \((.*)\)/',
+        'Mailjet' => '/[\d]{3} OK queued as (.*)/',
     ];
 
     /**
@@ -392,7 +393,6 @@ class SMTP
                 STREAM_CLIENT_CONNECT,
                 $socket_context
             );
-            restore_error_handler();
         } else {
             //Fall back to fsockopen which should work in more places, but is missing some features
             $this->edebug(
@@ -407,8 +407,8 @@ class SMTP
                 $errstr,
                 $timeout
             );
-            restore_error_handler();
         }
+        restore_error_handler();
 
         //Verify we connected properly
         if (!is_resource($connection)) {
@@ -483,7 +483,7 @@ class SMTP
      * @param string $username The user name
      * @param string $password The password
      * @param string $authtype The auth type (CRAM-MD5, PLAIN, LOGIN, XOAUTH2)
-     * @param OAuth  $OAuth    An optional OAuth instance for XOAUTH2 authentication
+     * @param OAuthTokenProvider $OAuth An optional OAuthTokenProvider instance for XOAUTH2 authentication
      *
      * @return bool True if successfully authenticated
      */
@@ -1170,7 +1170,7 @@ class SMTP
         if (!$this->server_caps) {
             $this->setError('No HELO/EHLO was sent');
 
-            return;
+            return null;
         }
 
         if (!array_key_exists($name, $this->server_caps)) {
@@ -1182,7 +1182,7 @@ class SMTP
             }
             $this->setError('HELO handshake was used; No information about server extensions available');
 
-            return;
+            return null;
         }
 
         return $this->server_caps[$name];
diff --git a/phpcs.xml b/phpcs.xml
index 9d174fab9..2d53b5996 100644
--- a/phpcs.xml
+++ b/phpcs.xml
@@ -5,7 +5,7 @@
 	<arg name="tab-width" value="4"/>
 	<exclude-pattern>./lib/CssXPath/</exclude-pattern>
 	<exclude-pattern>./lib/SimplePie/</exclude-pattern>
-	<exclude-pattern>./lib/PHPMailer/</exclude-pattern>
+	<exclude-pattern>./lib/phpmailer/</exclude-pattern>
 	<exclude-pattern>./lib/http-conditional.php</exclude-pattern>
 	<exclude-pattern>./node_modules/</exclude-pattern>
 	<exclude-pattern>./data/config.php</exclude-pattern>
diff --git a/phpstan.neon b/phpstan.neon
index 7f2749bad..99eac0e93 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -7,14 +7,14 @@ parameters:
 	paths:
 		- .
 	excludePaths:
-		- lib/PHPMailer/*
+		- lib/phpmailer/*
 		- lib/SimplePie/*
 		- node_modules/*
 		# TODO: include tests
 		- tests/*
 		- vendor/*
 	scanDirectories:
-		- lib/PHPMailer/
+		- lib/phpmailer/
 		- lib/SimplePie/
 	bootstrapFiles:
 		- cli/_cli.php
diff --git a/tests/lib/PHPMailer/PHPMailerTest.php b/tests/lib/PHPMailer/PHPMailerTest.php
new file mode 100644
index 000000000..4707e2a1e
--- /dev/null
+++ b/tests/lib/PHPMailer/PHPMailerTest.php
@@ -0,0 +1,8 @@
+<?php
+
+class PHPMailerTest extends PHPUnit\Framework\TestCase {
+
+	public function testPHPMailerClassExists() {
+		$this->assertTrue(class_exists('PHPMailer\\PHPMailer\\PHPMailer'));
+	}
+}