Yeah, it's finally done: I have migrated my primary MX to exim4 ! With only a 15 minutes downtime.

Since several month, I said that I will do it, and I did it ! I rewrote my exim3 conf for exim4. It was not too hard, but took me some hours to test it since my box delivers about 1k mails/days. It seems that everything is ok, but I am still tailling -f paniclog... :)