Hi all I am hosting about 100 email accounts, some moderately active. Every now and then a mailbox 'locks' and anyone sending a message to that box gets the response: Child process of virtual_sa_userdelivery transport returned 70 (could mean internal software error) from command: /usr/bin/spamassassin-cpanel ..and the message is never delivered as a result. This error only occurs when the file inbox.lock exists in the users' mailbox: inbox.lock --- 5 --- -rw-r--r-- Deleting the file frees the mailbox to start working again. This problem only occurs if SpamAssassin is enabled. A workaround for me is to use FTP Surfer (A free FTP client for Windows) and do a search for inbox.lock. Any that are found I check again a few minutes later and manually delete. I think that file is also created whilst a POP3 session is in progress; and might be left behind when a POP3 session hangs. Anyone else had this problem? Cheers, Mike.