Yup, tried zzn....
ZZN: I agree w/Koolguy & Nick, not so hot. But is reliable.
Outblaze: I have an account w/a place that uses Outblaze (i-p.com) a not good experience. All my affiliate correspondence was going to this provider & twice last year, ALL mail & files were wiped out, never to be seen again. Dunno' who's fault it was, but you can bet I'll never use Outblaze.
Everyone.net: I haven't heard any major complaints about them & they are generous re: revenue sharing. This one seems to be the new favorite among those I've talked to.
Here's an older one~
BigMailBox.com: pretty reliable. Yes, you use your own domain name. You're allowed to put 6 banners in rotation. Fairly configurable to the look & feel of your site. Gripe: support is slow to respond.
Since you're looking at ZZN, I take it you're interested in offering e-mail accounts to visitors. The following prolly won't be suitable~
BN3.com: no problems so far. Somewhat configurable, decent enough. Quick too. You can have up to 20 mailboxes under your domain. If you're lookin' to offer accounts to visitors, won't be many available.
Well, that's my penny's worth. Good luck, I hope you find something to meet your needs!
Later~
RR