If you want to access your E-Mails through GPRS with the built-in E-Mail client of the Sony Ericsson T68i I found a strange behavior but also a solution.
For any reason the T68i fails to connect the incoming Mail server right after it connected to GPRS. I've never had this problem with the Ericsson T68 but with the T68i now. The solution is pretty easy and worked for me very well:
Just add an additional CSD (Circuit Switched Data) account under Data Communication and use this account for the first time login to the mailbox. After the mobile phone received all E-Mails, switch your E-Mail account back to the GPRS account and try again - should works now.
You have to do this workaround every time you add a new E-Mail account, but for the first time connect only!
Cheers ~ Arne