Solution 1:-
1) Restart Quality Center to restart the SAQ thread
Make sure that all users are unable to send and receive e-mails manually. If users can send e-mail manually, then most likely the SAQ thread running in JBoss is either not started or not running. Check the debug info page to for the SAQ thread.
1. Check http://QCSERVER:port/sabin/servlet/tdsiteadminservlet?method=debuginfo
2. Find the following line; it will indicate the next time SAQ will run:
CSendAllQualifiedMailJob N 600000 13:40:12 com.mercury.td.saserver.jobs.CSendAllQualifiedMailJob@673757
If the SAQ thread does not appear or is not running at the specified time, restart Quality Center. Restarting Quality Center will force the thread to start.
Solurion2:-
If the FROM_EMAIL_ADDRESS for the specific project does not have a valid E-mail address specified.
Add the FROM_EMAIL_ADDRESS parameter to the DATACONST table for each project
To configure the e-mail address used for automatic e-mails in Quality Center 9.0, you can add the FROM_EMAIL_ADDRESS parameter to the DATACONST table of each project. The value given to this parameter should be the e-mail address to be used for automatic e-mails from this project.