Nope. Two possibilities:
1) Modify the sources.
2) Create a dovecot-auth proxying daemon. Login process connects to
your proxy, which in turn connects to dovecot-auth and just proxies
the data. Then whenever it sees that a login succeeds, it executes
whatever you want.
I'm not really planning on adding a post_login setting soon, since
mail_executable works for pretty much everyone. Have to think about
the proxying problem more before implementing anything.
My original idea was for my proxys to do some popbeforesmtp insertions into a database upon auth-success. Since the proxy knows the remote IP but the destination servers wont. My solution, for those that care, was to send my logging off to syslog, and have it execute a perl script which just listens for input. Grab the correct string via regex (from the wiki), make sure it's a non-local IP, and INSERT it into the table (going to switch to REPLACE syntax soon enough, so I dont have to worry about duplicates, nor tons of entries in my table). Seems to work fine with my current load. I'd be willing to share my hacks with any that might be interested.
Thanks,
-c