PHPMailer 6.9.1

This is a maintenance and feature release, adding support for the official release of PHP 8.3, methods for removing and replacing custom headers, XCLIENT support, and links to a new way of implementing XOAUTH2 authentication.

The only change likely to have any impact on existing code is that PHPMailer previously attempted to use opportunistic STARTTLS encryption when connecting to localhost, which was unlikely to work. The workaround required setting SMTPAutoTLS = false, but that's no longer required. You may still need to use this setting when connecting to literal IPs.

Changes

• Add support for official release of PHP 8.3, add experimental support for PHP 8.4
• Add clearCustomHeader and replaceCustomHeader methods
• Add support for the XCLIENT SMTP extension with setSMTPXclientAttribute and getSMTPXclientAttributes methods
• Don't attempt opportunistic TLS when connecting to localhost
• Add package link and example showing how to use @decomplexity's SendOauth2 wrapper
• Update example to show a better way of using an SMTP subclass
• Avoid some more deprecation warnings
• Update Danish and Polish translations
• Add Bengali and Assamese translations

Note: most of these changes were in the unreleased 6.9.0 version.