Yeah, since I haven't updated all the adapters we get runtime fatals loading them if these don't have default implementations. I'll remove these once I update all the adapters.

Yeah, the linter was complaining.

This is a pretty old rule out of T795 very long ago, which waffled a bit around @stable and then got swapped to @concrete-extensible later or something.

The original issue was that people kept sending us diffs to replace final/private/protected with public so they could extend random things in weird ways. In the cheery days of 2011 I was initially onboard with this, but soured quickly and moved toward "final absolutely everything we can".

Over time we made it to a world where every class is either abstract or final, and I think that's the right outcome. There's a linter to warn about cases which aren't abstract or final.

This class is "wrong": it should be final. However, SES extends it to use SMTP logic. An SES adapter is not a kind of PHPMailerLite adapter and this inheritance is definitely not "pure" or "correct", but I'll hopefully fix that a diff or two down the line and remove this comment/annotation/TODO, or fix it whenever T12404 happens if not here.

Ideally, we should get rid of all of these and then make the linter rule stop allowing the exception. We only have 8 left including this one, although some may be a bit tricky to exorcise.

D19965 eventually fixed these classtrees to get rid of the @concrete-extensible bit.

Relevant: http://steve-yegge.blogspot.com/2010/07/wikileaks-to-leak-5000-open-source-java.html