Probably, but not in the simple filter UI. The full Procmail module can almost certainly do it, though it’s been a while since I’ve looked at it, and it’s intimidating enough that you probably don’t want normal users using it (really, procmail is wildly complicated and the Usermin/Webmin UI doesn’t really solve that complexity).
Okay, thank you sir. I’ll research it. No need for you to waste your time on something that only a tiny fraction of users need. I have two non-rev domains that I use for sandboxing stuff like that (as well as for spam honeypots).
I have a client currently on cPanel who’ll likely need a new server within the next six months to a year. He has no issues with Virtualmin other than needing the functionality I mentioned above. I’ll take a look at it and see if I can come up with a template that works. It doesn’t have to be pretty because I’d be the one using it in production.
We’ll be adding support for Dovecot’s Pigeonhole Sieve interpreter, eventually (probably around about Virtualmin 8 next year, so not super soon), and I expect it’ll have a bit more capability than the current filters, and advanced usage of Sieve is a lot less intimidating and risky than Procmail even if you have to use it directly.