Hi Gil,
I was offering you a chance for testing your problem by using my own SMTP channel for 2 days.
And honestly, I had expected at least one small answer like: I works. Or it doesn't work.

Thus, as you don't seem to be interested in solving this issue any more I have removed that SMTP account now.

Hi Gil,

to sort things out (is your machine special? or does OSSN mail has problems?)

I will send you the smtp credentials I'm currently using successfully on newblue.ongolito.net

I will send it to the address you have registered here in a few minutes ...

If this channel is working for you, too, we had to investigate what's special with your office smtp
If it's not working, there must be something special with your host

I confirm I have to 1.1 verison of this module.

my /var/log/mail.err have a bunch of :
>May 10 14:39:06 RenoAQT sSMTP[24484]: Server didn't like our AUTH LOGIN (504 5.7.4 Unrecognized authentication type [HE1PR0101CA0023.eurprd01.prod.exchangelabs.com])

But I didn't use ssmtp anymore with this module right ?
I will uninstall it and check again.

I'm sorry Gil,
but currently I have no idea what's going wrong at your side.

Can you confirm, that you are running SMTP component 1.1. ?

I'm not quite sure because your checksum is different from mine. But there's a still a bug in the checksum calculation - but that's another story. I'll put an update on the server this evening.

Maybe you can find something in your smtp log file in the meantime.

And : https://framadrop.org/r/y_CtMdtanN#E3LW5+jZUms9UTl8lg4QuElGD60rw5+xNYTxdqsZZY4=

My bad I tried to edit my post without success.

I added the SMTP module for an easier setting up of the mail part since I post this.

I put the correct credential and it still not working.

I also install on this server to benchmark HumHub. And with the same credential this service is working well to send email.

Here a screen shot : https://framadrop.org/r/4rsk1oW2cl#wlMovRnBFGOHyab+bTiI0ic7MXk3KAOfFkUxsU0ODPk=

I'm not sure whether I understand your configuration correctly ...
I looks like you are trying to use your ubuntu machine as smtp relay with a message flow like

Ossn Smtp Component --> ssmtp on Ubuntu --> smtp on Company server --> outer world

So why don't you let the Ossn Smtp Component connect directly to your company server? Like

Ossn Smtp Component --> smtp on company server --> outer world

Simply entering the SMTP credentials of the company's server into the Ossn Smtp Component is sufficient. You don't need an extra relay on the Ossn machine.

In any case: Check your server's firewall settings to allow traffic on the used ports.