A maintenance update with a few minor feature additions.
This is officially the last feature release of the 5.2.x line. Security fixes only from now on; use PHPMailer 6.0!
- Added ability to extract SMTP transaction ID from successful submissions
- Allow DKIM private key to be provided as a string
- Provide mechanism to allow overriding of boundary and message ID creation
- Improve Brazilian Portuguese, Spanish, Swedish, Romanian, and German translations
- PHP 7.1 support for Travis-CI
- Fix some language codes
- Add security notices
- Improve DKIM compatibility in older PHP versions
- Improve trapping and capture of SMTP connection errors
- Improve passthrough of error levels for debug output