For some reason my log files are writing to the *.log.1 files instead of the *.log files, e.g. for my Postfix log files it is writing to /var/log/mail.log.1 and not /var/log/mail.log as expected. Same goes for mail.err.

It looks like it's also doing it for auth.log and syslog. Here is a ls -lt snippet of my /var/log directory, showing the more recently touched log files in reverse chronological order

-rw-r----- 1 syslog    adm      4608882 Dec 18 12:12 auth.log.1
-rw-r----- 1 syslog    adm      4445258 Dec 18 12:12 syslog.1
-rw-r----- 1 syslog    adm      2687708 Dec 18 12:11 mail.log.1
-rw-r----- 1 root      adm       223033 Dec 18 12:04 denyhosts
-rw-r--r-- 1 root      root       56631 Dec 18 11:40 dpkg.log
-rw-rw-r-- 1 root      utmp      292584 Dec 18 11:39 lastlog
-rw-rw-r-- 1 root      utmp        9216 Dec 18 11:39 wtmp
...

And ls -l mail.log*:

-rw-r----- 1 syslog adm       0 Dec 16 06:31 mail.log
-rw-r----- 1 syslog adm 2699809 Dec 18 12:28 mail.log.1
-rw-r----- 1 syslog adm  331704 Dec  9 06:45 mail.log.2.gz
-rw-r----- 1 syslog adm  235751 Dec  2 06:40 mail.log.3.gz

Is there something that is misconfigured? I tried restarting postfix and it still wrote to mail.log.1 afterwards (same with a postix stop; postfix start, too).