Getting email logs that show the following?

mail qmail-queue-handlers[8672]: Handlers Filter before-queue for qmail started …Jul 7 14:17:18 mail qmail-queue-handlers[8672]: from=domain@domain.comJul 7 14:17:18 mail qmail-queue-handlers[8672]: to=domain@domain.comJul 7 14:17:18 mail greylisting filter[8673]: Starting greylisting filter…Jul 7 14:17:18 mail qmail-queue-handlers[8672]: handlers_stderr: DEFERJul 7 14:17:18 mail qmail-queue-handlers[8672]: DEFER during call ‘grey’ handlerJul 7 14:17:26 mail pop3d: Connection, ip=[::ffff:203.197.xx.xx]Jul 7 14:17:26 mail pop3d: LOGOUT, ip=[::ffff:203.197.xx.xx]

In this case its referring to greylisting which you can choose to disable if you wish, http://kb.parallels.com/en/6359 is an article that refers to it.

Or run:

/usr/local/psa/bin/grey_listing --update-server -status off