Call for help

Hey, any Mac users who use Entourage for e-mail? Co-worker of mine is trying to send out a mass e-mail with several attachments, and people receiving the message were calling back, saying that they couldn't read it because it was in MIME format. Is there any way that anyone knows to solve that particular problem?

I wish I had more specifics on it. But this is the part of computer guru-dom where I am totally deficient. And since a lot of people on my flist use Macs ... well, any help would be useful.

Thanks!

ETA: help received. Crisis in abeyance. Thanks!