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

Symptoms

• An error that is similar to the following is displayed in the browser when trying to send an email from Roundcube webmail in Plesk:
  

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

• An error that is similar to the following is recorded in the /var/log/maillog:
  

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

Cause

The sender domain is blacklisted in Tools & Settings > Mail Server Settings > Black List:

Resolution

1. Log into Plesk
2. Go to Tools & Settings > Mail Server Settings > Black List
3. Select the domain tied to the sender email address and press Remove