Plesk mail sent to Yahoo is not delivered: Messages temporarily deferred due to unexpected volume or user complaints

Symptoms

• Email messages sent to Yahoo email addresses from a Plesk server aren't delivered

• These entries are logged to the mail log: /var/log/maillog

  [TSS04] Messages from 203.0.113.2 temporarily deferred due to unexpected volume or user complaints - 4.16.55.1; see https://postmaster.yahooinc.com/error-codes (in reply to MAIL FROM command))

Cause

Yahoo has blocked the server or its IP address in its internal blacklist.

Resolution

To get clarification on this issue, contact Yahoo Support for more details.
The following guide has a more in-depth look into this problem, along with steps that may help resolve the issue: An IP address of a Plesk mail server got blacklisted. How to troubleshoot?