Hmmm... a suggestion, though I do not know how viable it is as I do not know the underlying software well enough to know...
Can all the accounts on New TFF without emails be locked from posting until they put in an email... perhaps PM sent to each violator...
That would prevent this from occurring again I would think unless it is a first time log in. Perhaps a note in the new users thread if not already present that they need to do it... rather than threads, word of mouth, and even banner at top... since they don't seem effective.