The self-sent handling from #703 (reply to your own thread message ->
address the original recipients, ignore Reply-To) was entered whenever
From matched one of the user's identities. Contact-form / helpdesk mail
commonly arrives From the user's own address with the real correspondent
in Reply-To, so that branch ignored the Reply-To and looped the reply
back to the user's own To.
Only take the self-sent branch when there is no EXTERNAL Reply-To: a
Reply-To resolving to a non-own address is an explicit RFC 5322 directive
and now wins even for self-sent messages (#776). A Reply-To that is only
our own address stays ignored for self-sent (#703 preserved).
Closes#776.
Stefan Hildebrandt
Linus Rath