moderation of club emails

Is it possible to make it so that emails that go to various club emails are moderated? 

For example, occasionally we have club members who send out unsolicited marketing to the club. Is there a way to make it so that emails to the club - membership - need to be approved first?

Sorry no, toastmasters is an honour based system. We do have ways of blocking external mail.

Those members are breaking their membership agreement that they signed when they joined. Your executive should be reminding them of that fact and if they don't stop they should be disciplined up to and including dismissal from the club.