Question : Problem: iPhone imap sync on WiFi and 3G possible?

Hello once again experts,
Here is the scenario:

MS SBS 2003 w/exchange sp2 installed
using IMAP to sync to allow users to sync with iPhones.

When using 3G
Incoming Mail settings
Server:  mail.company.net
User Name:  [email protected] (internal)
Password: User password
Outgoing Mail settings
cwmx.com
no user id
no pass
no ssl
port 587

Got settings per this article:  http://www.experts-exchange.com/Apple/Software/Q_22735593.html

All works fine.

When using WiFi I'm still able to receive, but not send.  I've only tested this out on one wifi network so far, so I'm thinking it might be the ISP?  Its a Commercial Comcast account.  Seem to have trouble getting anything out on 587 though (not just iphone).  I'm thinking if I try going to a WiFi who's ISP isn't Comcast all is going to work well?

if this is a Comcast issue, does anyone know a way around this so that cwmx.com can get out through 587?  Or does anyone have any other suggestions getting the iphone to work with both wifi and 3g using the same smtp server?

Please let me know if I need to clarify more.

Answer : Problem: iPhone imap sync on WiFi and 3G possible?

It is not uncommon for carriers to block certain services over their celluar network.

Can I ask why you are using IMAP and not active sync. As active sync uses http then carriers shouldn't block this.