ePolicy Orchestrator cannot send Notification or Response email to web-based services such as Gmail, Hotmail, or Office 365 Technical Articles ID: KB60405 Last Modified: 9/12/2016
Are you blocking SMTP on the ePO server?
VirusScan Enterprise 8.x Access Protection rule blocks outbound SMTP mail on Port 25 Technical Articles ID: KB50707 Last Modified: 11/3/2016
Couple of other areas to confirm:
- Has the ePO server been added to your SMTP mail server white-list
- ePO Server <> Configuration <> Server Settings <> Email Server: Test email
- Can it connect to your SMTP mail server - Connect to your mail server - SMTP communicates over port 25. Attempt to use TELNET to connect to your mail server.