Email is delivered with a delay

Symptoms

• Email is delivered with a delay.

• The following rows appear in the /var/log/maillog file:

  CONFIG_TEXT: handlers_stderr: DEFER
  DEFER during call 'grey' handler
  Message aborted.
  milter-reject: DATA from mail.example.com[x.x.x.58]: 451 4.7.1 Service unavailable - try again later; from=<johndoe@example.com> to=<johndoe@example.org> proto=ESMTP helo=<mail.example.com>
  
  <...>
  
  Starting greylisting filter...
  handlers_stderr: SKIP
  SKIP during call 'grey' handler

  OR

  CONFIG_TEXT: greylisting filter[10489]: Starting greylisting filter...
  /usr/lib64/plesk-9.0/psa-pc-remote[8641]: handlers_stderr: REJECT
  /usr/lib64/plesk-9.0/psa-pc-remote[8641]: REJECT during call 'grey' handler
  /usr/lib64/plesk-9.0/psa-pc-remote[8641]: Message aborted.
  postfix/smtpd[10450]: reply: SMFIR_REJECT data 0 bytes
  postfix/smtpd[10450]: E612613C0057: milter-reject: DATA from unknown[203.0.113.2]: 550 5.7.1 Command rejected; from=<johndoe@example.com> to=<johndoe@example.org> proto=ESMTP helo=<mail.example.com>
  
  <...>
  
  Starting greylisting filter...
  handlers_stderr: SKIP
  SKIP during call 'grey' handler

  OR

  CONFIG_TEXT: Handlers Filter before-queue for qmail started ...
  from=johndoe@example.com
  to=johndoe@example.org
  Starting greylisting filter...
  handlers_stderr: DEFER
  DEFER during call 'grey' handler
  
  <...>
  
  Starting greylisting filter...
  handlers_stderr: SKIP
  SKIP during call 'grey' handler

Cause

This is expected the behavior of Greylisting.

Greylisting works as follows: the first message is rejected, and the next message sent from the same address (sender server IP address and 'From:') will be accepted after a certain length of time passes.

After the first email is rejected, the sender's address is added to the Greylisting database. The information is stored there for an expiration time interval.
For the message to be accepted, the grey interval must complete. If the message was sent before the grey interval has passed, the penalty interval is added.

Resolution

To prevent a delay, perform one of the following actions:

• Reduce the grey interval according to the following article:

  How to configure Greylisting?

• Add the required mailbox, e.g. johndoe@example.com, or the whole domain, e.g. *@example.com, to the white list at the Plesk > Tools & Settings > Spam Filter Settings > White List page.

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

• Disable Greylisting spam protection on the whole server by unmarking the Switch on server-wide greylisting spam protection checkbox at the Plesk > Tools & Settings > Spam Filter Settings page.

  Warning: this way reduces the protection from spam.

Additional information

• Antispam Tools

• Greylisting (Linux)

• How to configure Greylisting?

• The following statuses of Greylisting can be seen in the /var/log/maillog file:

  • "DEFER" means "Try again later"

  • "SKIP" means "Allow delivery"

  • "REJECT" means that the sender IP is blacklisted globally.