I finally got the evidence that Apples Mail.app from Leopard is causing the exceeding traffic I see on my root server. I mentioned this before in the podcast that there is something strange since the upgrade to MacOS X 10.5.
Since the update I got more traffic warnings from my provider. I didn’t believe this was due to increasing popularity of this blog and Google Analytics proofed that (unfortunatly). I then installed ntop traffic monitoring on my server to further track down the source of the exceeding traffic.
I had Apple Mail under suspicion because the problems started when some people around me and myself upgraded to Leopard.
Now I got the proof that this is caused by Mail.app. The new Mail.app in Leopard isn’t that stable and so it hangs from time to time. Then I can’t even quit it with forcing it to quit. So was this morning. Some of the Mail.app plugins stopped working and I decided to quit and restart Mail.app. But Mail.app hang during shutdown and wasn’t responding for more than 10 minutes. So I force quitted it and restartet Mail.app.
Everythings seems fine after restart. All my mailboxes where there, messages too and all the plugins where working properly.
But a few minutes after the restart I got another traffic warning from my provider stating that something had transfered 1 GB of data. I checked ntop and saw that this was IMAP traffic from my server to our office. So it was clear that this was caused by my cold started Mail.app
I also checked the system log of Leopard but didn’t found any usefull information on this behaviour of Mail.app. It seems that Mail.app had rescanned or even retransfered my whole IMAP mailbox due to this hard restart. But I can explain why that must happen.