huge exim_mainlog log file what to do ?

Hi my server have heavy mail usage .
So my exim_mainlog file under
/var/www/exim is getting very big.

I am processing this file using a MRTG script and displaying usage . So its very hard to grep data from this huge log file.

# ls -lh exim_mainlog*
-rw-r----- 1 mail mail 44M Sep 12 23:56 exim_mainlog
-rw-r----- 1 mail mail 83M Sep 7 04:02 exim_mainlog.1
-rw-r----- 1 mail mail 60M Aug 31 04:02 exim_mainlog.2
-rw-r----- 1 mail mail 10M Aug 24 04:02 exim_mainlog.3
-rw-r----- 1 mail mail 2.1M Aug 17 04:02 exim_mainlog.4

As I understand this log file is changing in 1 weeks time.
How can I force it to change everday?

Hello,

edit /etc/logrotate.conf

and change "weekly" to "daily"

John