FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
This article addresses issues with the configuration of the alertmail feature with Gmail when using FortiOS v4.0.
FortiOS Version 4.0
The alertmail feature cannot send alert emails using Gmail even though the ports are set to 465 or 587.
The alertmail service on the FortiGate is a simple proxy which supports only SMTP and does not support SMTPS.
Gmail requires TLS or SSL for the SMTP service, so it is SMTPS and not SMTP. The "set port" CLI command under "config system alertmail" is for SMTP protocol only. SMTPS is another protocol and Gmail SMTPS settings are not supported in the alertmail settings on the FortiGate.