Raulken has issued a fix on .com for the email problems.

Activiation emails, mass emails and back-up emails should be getting through much better now, but please be aware that this does not solve the problem of some ISPs blocking emails coming from ForumUp.

Of course this will not effect any emails sent before now.

Once this testing period is complete on .com (just about a week or so to make sure the fix works), I'll report back to Raulken and he'll add it to all ForumUp okay?

I am finally able to use the mass e-mail feature for the first time since my forum was created. I sent one to my users this afternoon and I'm receiving answers. Thanks Raulken.