[Dovecot] Mail history function?

I'm a newbie at Dovecot. For a company groupware I need a kind of a history function for mails to see which user sent which mail to whom / got which mail from whom. So I have to get the message ID of in- and outgoing mails (and write related data to a mysql database). My first idea was to monitor the log file with a daemon and search for strings like "deliver(x@y.z): 2010-11-15 17:34:56 Info: msgid=<AANLkTikoRgUiEg2KgUW2gLmULD4TX-bPst4yhUbuHoEH@a.b>". I'm not sure if this is the right approach. Does anyone know a better solution with Dovecot?

thanks, Oliver