My apologies - I misread. I'm sure that isn't possible. It appears to me to be a very rare use case and something I doubt would be added to Zimbra (I don't work for them, just a long-time user giving my educated guess).
Originally Posted by gantscha
The best I can suggest is the following. If your folders are set such that they are organized by subject, sender, or recipient (for example, mail from email@example.com is placed in the "John" folder, or mail with "ABC" in the subject is placed in the ABC folder), then you can still setup outgoing rules for this matching the same criteria. Using the previous example, if sender is 'firstname.lastname@example.org' then the outgoing filter would look for recipient = the same.
Note: if your folders are not setup by rules are are setup by a user or users manually moving mail to separate folders then this won't work of course.
State University of New York at New Paltz