10.3.7 and [snail] Mail

Many of you guys have noticed a serious speed issue with Mail.app and iChat.app after updating to 10.3.7. We couldn't isolate the causes, but it's obviously tied to the network framework.
One of our forum members, pallaire, seems to have found a solution, at least on his machine

About the lag that occurs upon launching Mail.app on 10.3.7.
It seems to be related to DNS.
I connect through DHCP behind a router, with a G5 dual 2GHz.
After I filled in the info about the DNS servers of my ISP in the network preferences panel, the app launched instantly. (before I had to wait over a minute)