Problem with sending and receiving mail to the domain, how to fix it?

Question

CMS

Not so long ago, there was a problem with mail, before the server normally sent messages (notifications) to users by mail, then messages about sending errors began to arrive in the mail of the domain, now the domain (server) does not want to receive and send messages by email at all. The problem is in the DNS records of the domain, please help me to configure the DNS records of the domain correctly to receive and send mail. Thanks in advance!

spoiler

Answer 1

This can be implemented on woocommerce, I think there are "virtual goods" than a link to a playlist can be. Or some plugin of a personal account with finishing

Answer 2

https://www.mail-tester.com/ - send a letter here, it will show everything what is wrong with you.
although if you send via mail (), then it's not surprising. Must be via smtp

Answer 3

You also need to configure DKIM, ie. make an appropriate entry in the domain settings.
Here is a configuration tool dkimcore.org/tools
And look in the ISP-manager panel, you need to register the appropriate DKIM selector for the mail domain.

Answer 4

You have both a CNAME and an A record for mail, this is not allowed by the standard (CNAME must not be combined with any other record type), leave one (remove CNAME).
You have 3(!) SPF policies for the main domain. This is unacceptable, such an SPF is considered invalid, leave one.
"v=spf1 ip4:88.198.230.107~all"