>>>>Which firewall did you turn off? You may have 2 firewalls, Windows and in your office router
>>>>Also your ISP may block port 25 to prevent outbound mail spam
>>>>
>>>
>>>Good thinking. I'd turned off the Windows firewall. As far as I can tell, my router has only an inbound firewall, not an outbound one.
>>>
>>>But your other idea got to me run a port checker and sure enough, port 25 is closed. So now I have to figure out if I can open it, and if not, what else I could do to test this code (since port 25 isn't essential to the project, just to the approach I was trying to use for testing).
>>>
>>
>>Usually, ISP provide their own SMTP server when they block port 25.
>>Also, if you have business account, most likely you can ask them to unblock it
>
>I gave up on using that SMTP test server that uses port 25. Tried again with my Exchange server and got farther, but had authentication issues. Next, I'm going to try with one of my various other email addresses that may make things simpler.
>
>Tamar

I mean, it's ok to block outgoing port 25 - unprotected SMTP is deprecated for ages. None of my e mail providers accept connections on 25.
So you need to set up SSL/TLS (465) or STARTLS (587).

Usually the simplest idea is to look up the SMTP settings required by your local e mail program, and then learn how to use this in your API. If you do not use local e mail - check your provider, they have a page how to set things up for various programs.
Also note, a SMTP server where you are not registered, iow not your e mail provider where you have user/password etc set, might reject your connection because of your IP, if you do not own a static IP. Dynamic IP's are blacklisted by default.