Horde/IMP: The folder “sent-mail” was not created.

When trying to send an e-mail via Horde (Plesk webmail), you’ll get following message:

The folder "sent-mail" was not created. This is what the server said: Invalid mailbox name.

Another problem you can have is that when logging in to the webmail, the redirect to your inbox doesn’t work.

Cause: If you face this problem while creating the sent folder in horde on a linux Plesk server this means that the php has been upgraded to 5.3.6 or later version on that server and some of the horde webmail namespaces are not compatible with the php 5.3.6 version and hence you were getting that error every time you try to create a sent folder.

As a work around you need to edit the below two files to fix this error :

/usr/share/psa-horde/imp/lib/IMAP/Client.php line 576

Edit:

function namespace($additional = array())

With:

function plnamespace($additional = array())
/usr/share/psa-horde/imp/lib/Session.php line 295

Edit

$_SESSION['imp']['namespace'] = $imapclient->namespace($user_namespace);

With:

$_SESSION['imp']['namespace'] = $imapclient->plnamespace($user_namespace); 

Restart the httpd service on the server.

service httpd restart

Reference: Linuxspy.info