Could not reach SMTP server through my home computer

Hi everyone. I'm new here, so first things first ... hello to everyone.

I'm using the most current stable imscp on our vserver in Germany. Everything works absolutely flawless, to include sending & receiving from the web based emails service ... roundcube as well as rainloop. Haven't had time yet to play with the SQL settings, but aside from that all appears to be well. The problem that we're experiencing doesn't have so much to do with imscp, but I'm hoping that someone here can point me in the right direction.

I've spent the past couple of days reading my eyeballs off about smtp settings with Thunderbird, including the articles at the Mozilla site, and I can't figure out for the life of me why email works within the imscp webmail, but not on our Thunderbird. Receiving is no issue at all with Thunderbird, but every time that we try to send anything out ... we receive smtp error messages. I've tested and tested countless settings, smtp server specifically per domain, a default smtp server for all domains, test mail after test mail, etc. I believe the problem has to do with the default mail server ... which I'm not at all certain how the default smtp server in imscp is set up ???

Also, I noticed a new ??? setting in the updated imscp for YES/NO external mail servers. All of the domains have NO (greyed out) set as default. Could that be our problem? I've never noticed that setting in our older imscp. I'm hoping that whatever the standard installation default smtp server for imscp is ... will also work on our thunderbird emails ... if I only knew how to figure out the default setting.
SMTP port settings on imscp as well as thunderbird emails are all set to 587.
We have a server admin, but they're not real familair with imscp yet either.
My apologies for not posting a strict imscp issue here in the forum. Just don't know where to turn anymore ...

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Thanks for the response. I realize that the problem is on my end, mentioned as much in the post. Just don't know where else to turn. Our admin is pretty confounded at this point too. Set up an email for the admin and they tried getting it to work in their Thunderbird without any success. Crazy quirk going on somewhere ... ???
Here's a screenshot. Let's see if this works ...

.001neuer_netcupserver01p.png

Well, the screenshot shows the current setting. I've also tried the same setting while using "mail" instead of the smtp. I've tried every type of security option that Thunderbird allows, including normal password without any special security. This is insane. I've used imscp on 3 different servers during the past few years, but this is the first time that we can't figure out what the heck is going on. Our home computers are Linux (Mint) boxes and they're all connected with PIA vpn service. We've been using the vpn service for a year though. Never had any problems with that ...
Here's the screenshot you wanted ...

EDIT: I had my thunderbird set up that way too. Where you have the user/smtp server on the bottom, under the STARTTLS ... that's where I wasn't sure what to use since I have several email accounts set up on my thnderbird. How can I add a user to the default smtp server there, when I'm using several email accounts together?

.001neuer_netcupserver01q.png

Thanks. Not sure how to use that "dig" command. Did a copy/paste and received a syntax error because of the >> in the command.

Telnet command = telnet smtp.winriddance.com 587
Query response = Trying 37.120.191.251...
(that's the correct IP of the server)
Final response = telnet: Unable to connect to remote host: Connection timed out

I am and have been using smtp.winriddance.com with thunderbird port setting at 587

It looks to me like there's something "missing" on my home setup.
(probably the same thing that the admin is missing on their computer too)

EDIT: Okay, gotcha on the dig command. I'm not sure if posting the output of that would be appropriate since the result of "dig" shows a bunch of different IP numbers, possibly some that belong to hardware from other people?

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