I found a solution with google search. The host = smtp.domain.com or mail.domain.com. Username = [email protected]. Thank you very much for your help, 10/10 on the mail tester point.

I installed the SMTP add-on.SMTP host = localhost? Where can I find SMTP users? SMTP port = 25.

Thank you ¬Z¬Man

Ossn comes bundled with PHPmailer.
The default way of sending outgoing messages from Ossn is
[OSSN: your message -> PHPmailer] -> [YOUR PROVIDER: Apache's PHP module -> mailserver (sendmail, postfix, etc)] -> recipient

An alternative way is to configure PHPmailer to use SMTP like
[OSSN: your message -> PHPmailer] -> [3rd PARTY SMTP SERVER of your choice] -> recipient

Every SMTP server needs to be addressed correctly and you need an account to authentificate
Ossn has a dedicated frontend component to accomplish this task. It is available at
https://github.com/opensource-socialnetwork/SMTP

Download and install this component, then run Configure->SMTP and enter your credentials.
Search the web which way to use your own gmail account for that.

As soon as my registered members become 3,000, I’m looking for a provider right away, I don’t have the money for it.

How does sending OSSN email work? What does it depend on to send php sctipt or SMTP?

What kind of provider is that who does not feel responsible for its own services?!?
From your mail I saw it's https://www.hosting55.com.
Not even his knowledgebase is working,
https://www.hosting55.com/knowledgebase is unreachable!
To me the final signal to leave and find a serious one.

The information was sent by my service provider, but I can't find the setting in the cpanel. My provider doesn’t help, he says it’s not his business.

Az OSSN e-mail küldése hogyan működik? Min múlik, hogy php sctipt küldi el, vagy az SMTP?

Every CPanel may look different. So you'd better ask your provider. (or in a Cpanel forum)
Didn't you write: "My service provider sent the information to me" ?

Where can I configure cpanel to make "X" problems go away?

Yes, that's what I was trying to suggest.
At least these 2 lines

X-PHP-Script: elittag.hu/system/handlers/actions.php for 84.1.50.62
X-PHP-Originating-Script: 1032:class.phpmailer.php

The mail I sent to you had none of these lines, and you said it was received correctly. That's why I see a chance to try it this way first before installing an additional component.