After a lot of searching, I'm still clueless as to where the problem lies.
By the way, it does work with my system user, but for some reason I can't log in with that account in squirrelmail. It just doesn't accept my username/password.
When I send a mail to both type of accounts I can also see a difference in the mail.info log:
/etc/mail.info
Code:
May 22 17:55:24 mydomainname postfix/local[9895]: 5152556564: to=<rogier@otherdomainname.nl.eu.org>, relay=local, delay=2.4, delays=0.33/0.18/0/1.9, dsn=2.0.0, status=sent (delivered to maildir)
May 22 17:55:24 mydomainname postfix/pipe[9896]: D605A5655E: to=<user@mydomainname.com>, relay=maildrop, delay=3.6, delays=1.6/0.1/0/1.9, dsn=2.0.0, status=sent (delivered via maildrop service)
One is delivered to maildir, the other delivered via maildrop service.
From the google searches I made, I'm getting quite convinced that if the latter were working, the log would show that the mail directed to
user@
mydomainname.com
wouls be delivered to maildir as well instead of via maildrop service.
I hope this helps you guys who are trying to help me.