Answer
If the event action itself completed and logged in Application Messages, the actual sending problem is almost always downstream, in the Mail Sender connector configuration under Setup IFS Connect — most commonly an incorrect username/password on that connector, or a security-protocol mismatch (needing TLS or SSL where a different setting is configured). It's also common for the mail relay/Exchange server itself to need to be configured to allow anonymous relay specifically from the IFS application server's IP, since IFS may not be using a dedicated mailbox account to authenticate — check both the connector credentials/protocol and whether the receiving mail server actually permits relay from the IFS server before assuming the event configuration itself is at fault.