Symptoms

Task Notification Emails are not working on a Specific UAT Environment
 

Diagnoses

 The error is related to a bad configuration of MSMQ.
 

Resolution 

In an online session we performed the following steps.

1- uninstall then ReInstall MSMQ.
2- Run K2 Configuration Tool, Analyse all and fix anything is in red.
3- Configure connectionstringeditor.exe
3-1 Authentication: Windows
3-2 TLX: None.