You may occasionally have encountered a problem with Spam originating from one or more of your Cloud Servers. Aside from issues with being listed on RBLs, this will cause the server's mail queue to overflow, either because of the amount of generated mail that the server itself has been unable to process, or because of mail bounced back by the recipients themselves.
If your mail server is Qmail, you will not be able to delete the mail queue automatically and easily (even with Plesk, deleting the queue may not be possible depending on its size), so other methods should be used.
You must stop Qmail before deleting the queue, as errors could occur if you do not stop it. To stop the service, the following command should be sufficient:
# /etc/init.d/qmail stop
To delete the queue manually, you will need to recreate the Qmail queue directory structure as follows:
# cd /var/qmail/queue/
# rm -rf info intd local mess remote todo
# mkdir mess
# for i in `seq 0 22`; do mkdir -p mess/$i; done
# cp -r mess info
# cp -r mess intd
# cp -r mess local
# cp -r mess remote
# cp -r mess todo
# chmod -R 750 mess todo
# chown -R qmailq:qmail mess todo
# chmod -R 700 info intd local remote
# chown -R qmailq:qmail intd
# chown -R qmails:qmail info local remote
After running all the commands above, which should have completely emptied the mail queue, you can start the service again using the command:
# /etc/init.d/qmail start