blocking a specific email suffix

[Dirk]

I use suffixes on pretty much all of my email subscriptions, so my email address for google would be user-google@domain.tld and my email address for the zimbra forum would be user-zimbraforum@domain.tld etc.

I do this so that if I start to get lots of spam email to, lets say, user-microsoft@domain.ltd, then I'd know that microsoft had leaked my email out to bad guys, and I could block that address.

It's the blocking part that I'm struggling with though, there seems to be no way to blacklist a suffix. If would like to have it so that particular email address becomes invalid and is bounced. Currently I've added a filter to notice the address in a 'to' field and mark it as spam but this does not always work.

Is it possible?