Activating mail service on domain
STEPS
1. Access your Plesk control panel at https://www.yourdomain.com:8443 [ Example :https://www.crmcell.com:8443 ]
2. Click on Subscriptions.
3. Click on the control panel of that subscriptions.
4. Click on Mail tab.
5. Click on change settings.
6. Enable on Activate mail service on domain.
7. Click on ok.