We use FM extensively in our business. It's essentially become an ERP.
The ability to have our server and clients send emails has been a tremendous benefit. It's really extended the reach of our information and our communication loop.
As we know, the email client interface is not strong. The SMTP interface has been much smoother.
We moved our servers to AWS with our FMS as a traditional win server (not the FMcloud system). This server sits outside of the "DNZ". We also moved from a local MS Exchange server to MS Outlook 365. A local FMS and local Exchange server worked well together.
In doing that move, we are now routinely getting "refused by server" errors when trying to send email via SMTP. In many cases is seems to work, so the issue is intermittent.
We are using this for the Outgoing SMTP server "our_Name.mail.protection.outlook.com" with port 25.
We tried having a well know plugin FM developer try to implement SMTP via Amazon's SES with their plugin. That didn't work.
Our IT guys that set us up on Outlook 365 and AWS don't know much about FM.
We have given the Base Elements a brief try (unsuccessfully) but I'm hesitant after the experience with the other plugin.
I'd be happy to pay someone that has direct experience with this issue to solve it. A referral would be appreciated.