fetchmail in ispconfig 3.0.3.3

Dears Seniors,

I have ISPConfig 3.0.3.3 installed in Ubuntu 11.04 (as in here)

I want to get the old email on the old exchange mail server to the new postfix ISPConfig 3.0.3.3 (as backup restore)

I'm not able to use IP in field "Pop3/Imap Server", and if i pressed the save its giving "Pop3/Imap Server is not a valid domain name." So is there any way to do it? or is there a way to redirect any name to the required ip?

but which i feel it should be accepted because already i have test it in my pc.

i forget to mention that is they are both in same network and same local ip range.

Thanks in advance foe your help and support