Wordpress not sending mail after domain transfer?

Question

Mail server

Good afternoon! Already tried everything, googling half of Google and nothing helps.
I made a wordpress site initially on the laponka.rf domain, after the site was completed, I transferred it to laponka.ru. Since I'm still just learning, it turned out that the site had to be restored from a backup, since all site data was deleted. Further, there were problems with the fact that the images of the site were not displayed and this was solved.
Now the problem is that letters are not coming from the site. Not in spam either. Neither on yandex, nor on mail, nor on gmail, letters do not go anywhere. If you change the admin mail in the site control panel, then you do not receive a letter confirming the transition. Letters do not come through the ContactForm 7 feedback form either. As well as it is impossible to receive a letter with the registration of an account in woocomerce and with an order.
PHP Mailer works on the hosting, I wrote to the hoster and tested everything.
Changed email address in PHP.ini, no response.
The site was transferred according to this instruction in 3 ways: dimox.name/moving-the-site-on-new-domain
Maybe something else needs to be replaced?
In the htaccess file, I also found links to the old domain, replaced it with a new one. Did not help.
Where else to look? What else could be the problem? Maybe something needs to be enabled somewhere?
It’s impossible to set up via SMTP, since the domain and hosting are from different registrars, and there are some difficulties with the transfer. You need to have one registrar. We will do this transfer, but something tells me that even after that, mail will not come, since the problem seems to be in the settings of the wordpress itself or the SQl databases, something went wrong when transferring the domain.
Maybe there is a solution? I've looked all over the internet, nothing helped.

Answer 1

what is the problem anyway. kick a support
and more
the hoster may not allow you to use your MXs if the domain is not registered with him. it's by the way

Answer 2

So the problem is still in the hosting?