We've got an emeritus faculty member John Doe <email@example.com> and a new executive Jane A. Doe <firstname.lastname@example.org>. John keeps getting Jane's mail.
John actually prefers to have his email forwarded to Yahoo! Mail anyway. But he doesn't want to lose correspondence to his old address, since he's been email@example.com for more than 20 years.
What we'd like is for email sent to jdoe to have both a forward and a vacation autoreply disambiguating the two addresses ("If you want John, use firstname.lastname@example.org; if you want Jane, use email@example.com"). But it doesn't work. The forward trumps the autoreply.
I have also tried making a forward-then-discard rule. That doesn't work either. I tried Trash rather than Discard. That resulted in
2008-04-03 08:46:41,641 INFO [LmtpServer-25768] [firstname.lastname@example.org;mid=2488;] mailbox - outofoffice not sent (in trash) mid=9904 email@example.com'
All quite reasonable and correct, but not what I want in this specific case!
An autoreply set on the Yahoo! Mail end won't work, because (again, being quite reasonable and correct) Yahoo! Mail won't autoreply unless the yahoo.com address appears in To: or Cc:.