Email delivery fails: 5.7.1 Command rejected

Symptoms

• Email delivery to the mailbox on the Plesk server fails with the error below:

  said: 550 5.7.1 Command rejected (in reply to DATA command)
  Reporting-MTA: dns; 203-0-113-2.example.com

• The following messages can be found in /var/log/maillog file:

  greylisting filter[31260]: Remote host 203-0-113-2.example.com in black list

• Greylisting is enabled on the server.

Cause

Sender hostname matches greylisting blacklist pattern.

Resolution

1. Log into the server via SSH.

2. Whitelist sender domain using instructions from the article:

   • How to configure Greylisting