first things first - take your morals and put them in your pocket. Save it for someone else!
Sorry if that seems rude - it's not meant to be. But I can read about morals anywhere on this forum. I'm looking for facts!!
Now, that said, I've got in my tos the whole thang bout how we may check bulk mailings for content from time to time to protect our servers from spammers.
The question is...how would I do this?
I've found spammers by checking the mail queue after mail-watch notifies me of mass mailings. I find that the list spammers have usually have at least 1 bad email address. That sometimes causes it to get stuck in the mail queue as it's being bounced n such. Which allows me access to the contents
But what about others? For instance just an hour ago someone sent out 100 emails in 15 minutes. *yes could be anything - but lets not go into speculation*
If anything, I'd say that you're exercising good morals by trying to prevent your customers from spamming. I wish that more people did this!
Why not make a script that gets run from cron every five or ten minutes, examines the contents of the mail queue (you could grep for return addresses and store them in a hash), and then copies suspicious messages from the queue to a temporary directory, where you can inspect them later?