Connection to external mail source doesn't work - email notifications does not work

I haven't heard of any widespread issues like this. You may want to check if enabling logging would provide any additional information: Collecting Logs for Email Server Connections and Emails sent by M-Files Server

You didn't mention what M-Files version you are running. If you are running an older version, you may want to consider upgrading to the latest release in case there have been some fixes related to these mail server connections.

If you cannot resolve these issues yourself, I suggest contacting your M-Files reseller for further troubleshooting.

I haven't heard of any widespread issues like this. You may want to check if enabling logging would provide any additional information: Collecting Logs for Email Server Connections and Emails sent by M-Files Server

You didn't mention what M-Files version you are running. If you are running an older version, you may want to consider upgrading to the latest release in case there have been some fixes related to these mail server connections.

If you cannot resolve these issues yourself, I suggest contacting your M-Files reseller for further troubleshooting.

Thank you for your answer. we have the newest version of the M-Files. But I think that we solved the problem. This helped on our exchange server:

netsh interface ipv4 set subinterface “3” mtu=1450 store=persistent