Problems sending email - getting a strange usermin message: Failed to open /home/testdomain.dk/homes/dd/.tmp/...

Hi

Just reinstalled a server, and seems to have everything running, but email is giving me problems. To make sure it wasn't an issue when restoring my sites, I created a new testsite and a mail user for that site.

When I log into usermin and want to compose a message, I'm seeing this message: Failed to open /home/testdomain.dk/homes/dd/.tmp/.tmp_MTM4NzMxMzc4NQ_usermin_redirected_dd.testdomain.dk for writing : No such file or directory

Anyone know how to fix this issue?