@falco: ok, i deleted it and restarted postfix
important: the client just came back to me and he said the folder /home/vmail has to has owner "vmail". once he change that, i received a new error message from quirrelmail:
Error opening ../config/default_pref
Could not create initial preference file!
/var/lib/squirrelmail/data/ should be writable by user www-data
Please contact your system administrator and report this error.
i then went to the folder /var/lib/squirrelmail/data/ and tried to change its permission, but the only way that didn't turn back the same error message was 777 - well, I didn't try all versions to be honest, so what do you think, what should it be set to? also, what account should be the owner of this folder? currently it's set to vmail
once i logged in i could see the email list (well, actually it was empty) in the middle but on the left hand side it gave following error:
ERROR: Could not complete request.
Query: CREATE "INBOX.Sent"
Reason Given: Cannot create this folder.
I tried to give the .Sent (hidden) folder in /home/vmail 777 permission but that didn't help (it was on 700) still owned by vmail
i tested sending and it worked, then i replied but that bounced back with error
The error that the other server returned was: 550 550 5.1.1 <email@example.com>: Recipient address rejected: User unknown in virtual mailbox table (state 14).
also, the documentation says that when i create a new mailbox and send an e-mail to it with mailx, it will create a mailbox in vmail. well, i tested that and it did not work, can you help there? If i remember well i had to create the folder myself. now, after i tried to login there, i can see that it created a hidden .Sent folder but nothing else and also it displays the folder not found error in the middle (i guess it's looking for the non-existing Inbox folder) like the for the above, working account for the sent folder.
i'm getting close, your help would be soooo much appreciated!