SMTP e-secure with authentication

Hello Meriam

FortiGate supports authentication over SMTPS/SMTP/STARTTLS.

If e-Secure supports the same then they should be compatible.

Check the first section in the following page:

https://docs.fortinet.com/document/fortigate/7.4.2/administration-guide/526019/email-alerts

SMTP is a standard protocol and esecure is one vendor using SMTP like many other, Fortinet has no special use/change to SMTP.

As AEK mentioned, FortiGate supports authentication of SMTP and its TLS variants SMTPS/SMTP STARTTLS. There is no need for any plugin, you should follow the documentation on the email alerts shared by AEK.