As https://secure.phabricator.com/T12404 has not magically appeared right around the corner, we have a 14 year old copy of PHPMailer in the stack, added in January 2011, (with a small number of custom downstream patches on top).

https://secure.phabricator.com/T12046#205086 implies that upstream moved from Sourceforge to https://github.com/PHPMailer/PHPMailer/ at some point.

I remain clueless where our "Lite" version originally came from. In upstream, the only reference I could find to a "Lite" version is the removal of some references in https://github.com/PHPMailer/PHPMailer/commit/019499efc3402cf651f7e6080e7d7bd19076a922. (I admit I did not try to dig up things in SourceForge though.)

The other three PHPMailer files (non-lite, pop3, smtp) got added in Dec 2012 to "support SMTP" in https://we.phorge.it/rPf5c2a2ab4bbe6317993fbcb406a86993e6ab75e0 . Again, such differentiation is long gone in upstream (which had several file renames and moving stuff around too).

Our first downstream versions of lite and non-lite seem to closest resemble upstream https://github.com/PHPMailer/PHPMailer/blob/5b661107cab6ae3d96a076532c8fccf23ea07ece/class.phpmailer.php when it comes to upstream history.

Running a diff between lite and non-lite in our downstream, I do not spot large differences hard to overcome, so we should get rid of that "lite" version to reduce long-term maintenance costs.

./phorge/src/applications/metamta/adapter/PhabricatorMailAmazonSESAdapter.php:    require_once $root.'/externals/phpmailer/class.phpmailer-lite.php';
./phorge/src/applications/metamta/adapter/PhabricatorMailSendmailAdapter.php:    require_once $root.'/externals/phpmailer/class.phpmailer-lite.php';
./phorge/src/applications/metamta/adapter/PhabricatorMailSMTPAdapter.php:    require_once $root.'/externals/phpmailer/class.phpmailer.php';