1. Sounds like voip stuff
2. Mail server...Putting a host on a lan and routing that segment...I'm all over that.
3. 5800 doing a bunch of voip...I plead the 5th.
4. They dial into a mail server? Do you mean a voicemail server?
5. Download thier mails? Over voip? How?
6. Like I said, I'm voip clueless.
Since I'm your only response, I would hit up cisco-nas@external.cisco.com and cisco-voice@external.cisco.com for some help.
Or...maybe someone will jump in since i gave such a lame reply :)
Josh