Article ID: 125397, created on May 2, 2015, last review on Oct 17, 2016

  • Applies to:
  • Plesk 12.5 for Linux
  • Plesk 12.0 for Linux
  • Plesk 11.0 for Linux
  • Plesk 11.5 for Linux
  • Plesk 10.4 for Linux/Unix
  • Plesk 12.5 for Windows


Email is not delivered. The following messages are shown in the /var/log/maillog log:

handlers_stderr: DEFER
DEFER during call 'grey' handler
Message aborted.
milter-reject: DATA from[x.x.x.58]: 451 4.7.1 Service unavailable - try again later; from=<> to=<> proto=ESMTP helo=<>


Handlers Filter before-queue for qmail started ...
Starting greylisting filter...
handlers_stderr: DEFER
DEFER during call 'grey' handler

After a while, email finally arrives into the mailbox with the following entries in /var/log/maillog log:

Starting greylisting filter...
handlers_stderr: SKIP
SKIP during call 'grey' handler


This is an expected behavior of Greylisting that introduces a short delay before accepting mail: mail gets deferred for the first time, then gets delivered for the second attempt to send an email. In most cases, mail from a valid sender will be delivered within an hour, but depending on how the sending server is configured, it could be much longer.

Mail from a spammer, on the other hand, will be deferred for 1 time and mail sending will not be retried: spammers usually send mail in bulk to thousands of recipients and do not bother with resending. See Plesk Administrator Guide for more details.

Delay takes place because Greylisting verifies three components of message: IP, sender, recipient. Based on these components Greylisting determines whether it should issue a temporary reject code or accept the message.


To prevent delay, put required mailbox or the whole domain * into White List in:

Tools and Settings > Spam Filter > White List

This way email from the white-listed senders will be accepted without passing through the greylisting check.

Alternatively, disable Greylisting spam protection on the whole server:

Tools and Settings > Spam Filter > Switch on server-wide greylisting spam protection

Additional information

The following statuses can be seen in maillog: DEFER, SKIP, REJECT

In terms of Greylisting DEFER means 'try again later'; SKIP means 'allow delivery'; REJECT means that the sender IP is blacklisted globally.

Search Words


Unable to receive an email

Sometimes our Plesk rejects mails coming from external mail servers to domains hosted on our Plesk

Message aborted

FastCGI-stderr: PleskUtilException: /usr/local/psa/admin/bin/mailmng '--start-milter' failed with message: mailmng: Unknown option in command string, see log for details

Greylisting referrs mails but greylisting is disabled for these domains

DEFER during call 'grey' handler

Greylisting works but it is disabled

Mail is delivered with delay from particular senders

451 4.7.1 Service unavailable - try again later

Outgoing Mail Limit Causes Delay

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