This event was not reflected in error_log, I looked. What could be the problem?
Did I fill in the settings correctly? I was definitely not mistaken with the login and password of my gmail.

Make sure to show php errors and try ie registration that send email.

Yesterday's 500 Error got into the report, but today's (non-sending mail) was not reflected in the report. What does ie registration mean?

When registering, email is sent. If mail is not configured properly, it will throw error.

I set up an email account with my hosting cpanel and sending emails started working with it. Doesn't work with Gmail. Thanks for the help!

@alex7070
It does work with gmail for me 

Your hosting enable Apache Module mod_ssl?

@alex7070
No it does not support apache module mod_ssl.

As I always SAY SSL is not working ( mostly because the error " mod_ssl " ). But even with working one it will still not work in SSL. So leave the field empty and will start working. P.S. For some reason in the last versions ( not only the version of Osclasspoint but in other versions too ) google email server is not working in OC

Foe me gmail works.
Ssl auth is dependant on hosting, I do not think there is relation between mid_ssl and ssl auth not functional.
Ie on my hosting ssl create delay when sending mail, anyway I will try to reserve time to look on it

Try with blank on ssl, just delete the ssl in the text area and leave it blank it will work

In any case, sending via gmail is unreliable. They can make restrictions in case the emails seem suspicious to them or there are a lot of them. Better to use for sending smtp of hosting.

@alex7070
I know cases where hosting can do the same, it happened to me few times, just some people marked mail as spam and it stopped to work

Have you tried sending mail via yahoo? It doesn't work for me with either yahoo or gmail. Maybe something is wrong with my hosting.

Well, ie for gmail I remeber I had to specially allow using account for sending mails from application.