VPN Users (CISCO) on iOS cannont send Email via SMTP

Hi there,

we have a big problem with our iPhones and sending E-Mails via SMTP.
The iPhones do connect to our LAN via CiscoVPN and get a static IP-Adress.

We have an internal e-Mail-server (KOLAB), where AppleMAIL on the iPhone connects to.

When i use AppleMAIL on the iphone, i receive new E-Mails via IMAP, but AppleMail won`t send E-Mails via SMTP.

Both Proxies on the Sophos, SMTP and POP are enabled.

Can anyone help?

Thanks in advance!

Lars