How to proceed with using smtp in custom windows applications

[oldbob1938]

We're a small non-profit and we use custom apps to send monthly newsletters to our membership, to inform office staff of completed operations by automated programs.  Using 2 factor app passwords doesn't work as the app has no way to respond.  We have a phantom "user" named messenger who sends the status emails automatically upon completion/failure of tasks.  This has worked successfully for us for over a decade.  Am not sure how to proceed.  Suggestions are welcome.

[KAM]

@oldbob1938 you will want to look at this and ideally transition to OAuth: https://support.google.com/a/answer/14114704?hl=en

There are also other places that can provide SMTP relay that you might want to look into called ESPs that might be worth looking at.

-KAM