Maybe your smtp host is blocking the connection? Can you try your connection to the SMTP server using other services or apps?
Also, are you using the self-hosted version or the cloud version?
@kemoso, it’s hard to say for certain with out a little more detail, but I had this error when connecting my outlook account some time ago. It seems that using the TLS port number, if I ticked TLS alongside it, it would timeout every time the same with the non TLS port. Out of curiousty, I tried the TLS port number without ticking the TLS box and it connected instantly, I tried a few test mails and they all sent and were received without issue.
@kemoso If you want to use Gmail ( or your own domain but using Google Workspace )for sending the emails , I think you can use the “Gmail” Piece, is so much easy and fast.