If you got a problem on any other server than the official ones, you can still make a thread here, but it would be the best to contact the serveradmin or post on the servers own forum/website.
Also note that your thread is most likely going to get deleted after your issue has been resolved, to keep the forum clean of "I've been banned!" threads.
Below is a list of the official oc servers and a contact list of other server admins.
Banlist
Contactlist for non-official servers
Z-server
Admin: Zteer
Website: http://z-server.bbs.coocan.jp/
[JP]syonbori server
Admin: Masa0x/ コンバット越前
Website: http://blog.livedoor.jp/cbt_echizen/
List may get expanded later.