Unverified users I remove monthly.
We usually get a average of 20 daily spammers also that the mod catches that need to be checked and removed as well.
I can filer out newbies and other members by status but only the senior member and hero member groups have a low enough count for auto emailing.
That is the only way a email send can be limited with the version of the forum currently running. There may be a mod available to further limit sends but installing one is something I can't do.
The new company IT guy has enough issues on the go right now with out having email bog downs.
Most of the contributing members get notice when a thread they posted to gets a new post anyways.
Some users also setup a special email address just for the forum and have since removed it.