Yes, it would work, now that
Bug 37164 - mail filed into Junk by Filters is not used to train anti-spam has been fixed.
Simply advertise your bogus email account, and create a filter as you say, that files all incoming mail into Junk. You'll also want to give the account a COS that purges Junk more frequently than normal, just to keep the account from filling up.
The only issue here is that if a message is marked as spam by Zimbra's SpamAssassin, then it will go straight to Junk and it will NOT be used to train the antispam system except if it has certain characteristics. (I believe the criteria are: must score 3 or higher in both header and body tests. See
AutolearningNotWorking - Spamassassin Wiki and my posts in
More Spam after upgrading to 6.0.5)
You could probably find a way to force autotraining for
all mail that comes to your honeypot account. Possibly if you set zimbraSpamApplyUserFilters TRUE on a given account or COS via zmprov (as described at
Bug 34039 - RFE: Option to apply mail filters on Junk Folder), you could have that interact with 37164.
If you do this, then you can take advantage of the honeypot in another way: use it as a "spamtrap". Although this term is sometimes used synonymously with honeypot, here the idea is somewhat different. What you would do is create a SpamAssassin rule that assigns a high score to any mail that is addressed to the spamtrap address. This way if a spammer tries to deliver an email to multiple addresses in a single SMTP transaction, the presence of the spamtrap address in the list will be an immediate indicator of spamminess.
If you try any of these ideas, please post a followup in this thread to let us know how it goes!