Environment
GroupWise 18
Situation
When trying to send an email using GroupWise Web an E51C error occurs.
Resolution
E51C errors indicate a space restriction on the mailbox has been reached and the user has no disk space quota left.
Either reduce the size of the mailbox or increase the disk space quota. Once done, run GWCheck with "Update user disk space totals" selected under "Fix Problems"
Cause
Disk space quota had been reached so no disk space was left for the mail to be sent.