Fortigate doesn't send the alerts

For the printer account have your setup SMTP AUTH in the office365 portal?  This blog article outlines a setup for office365.  The other item they had differently is the default reply to address was the same as the username.  You may need to verify permissions in office365 if that user can send as the is user.

https://aventistech.com/kb/email-alert-with-office-365-in-fortios-6-4/

Going to offer a possible alternative solution for now or future use. Due to our size and the amount of devices I had that needed to send email (i.e.. MFP copiers, various appliances for email alerting, etc...), I setup a internal mail relay (I use my old Barracuda SPAM firewall to do this but you can utilize whatever is more available to you). I have a VIP to this device and a corresponding egress policy for outbound SMTP traffic only. Office365 has a a rule for this public IP and that IP is in my SPF DNS record. I just point my devices to my internal relay host at port 25 and that's all that's needed. Leaving out a lot of steps, but you get the general idea.

I still not receive alerts from fortigate but saturday I received 3 alert emails.
The timestamp of emails matches exactly with another error with wan2 port.

Maybe the error is from static routes?