Unable to send emails from a particular domain in Plesk: SMTP Error (554): Failed to add recipient: Sender address rejected: Access denied)

Symptoms

• The following error message occurs, when trying to send an email from Roundcube:
  

  CONFIG_TEXT: SMTP Error (554): Failed to add recipient "john.doe@example1.com" (5.7.1 <bob.doe@example2.com>: Sender address rejected: Access denied).

• In /var/log/maillog the following record accompanies failed sending:
  

  CONFIG_TEXT: NOQUEUE: reject: RCPT from localhost[::1]: 554 5.7.1 <bob.doe@example2.com>: Sender address rejected: Access denied; from=<bob.doe@example2.com> to=<john.doe@example1.com> proto=ESMTP helo= 

• Affected domain is listed in Plesk > Tools & Settings > Mail Server Settings > Black List:
  

Cause

It is prohibited to send and receive emails for a blacklisted domain. 

Resolution

1. Log into Plesk;
2. Remove the affected domain example2.com at Tools & Settings > Mail Server Settings > Black List.