With IPHost Network Monitor you can run simple snmp requests against a Fortinet device in your network.
fnAvCfgBlkEmailSmtp
fn Av Configure Blk Email Smtp
1.3.6.1.4.1.12356.6.3.9
The email will be blocked if the email size over the limit, which is in terms of the percentage of the memory size (2M).
Back to FORTINET-MIB MIB page.
IPHost Network monitor allows you to monitor fnAvCfgBlkEmailSmtp on Fortinet device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Fortinet WAN extenders right now.