How to understand the DNS settings of a hoster and a domain registrar?

Question

Domain Name System

The problem is that I can not set up sending mail from my host.
There is a domain registrar, I buy hosting from another organization.
I deploy the project scripts on the hosting, the domain is available, everything is fine with the scripts, but as soon as it comes to the fact that the script should send out the registration data of registered users, I get a complete misunderstanding of this process. Mail does not go to external servers.
I would like some advice on how you set up your servers when you buy a domain from one organization and buy hosting from another.
In particular, the registrar of the hoster.kz domain name, the hosts are American and Canadian servers.
I realized that I have an absolute mess when setting up name records.
I can’t fully understand what I’m setting up on the side of the domain name registrar, and what should I set up at the hoster.
Who will help with advice from their experience so that my porridge in my head is cooked. And preferably on the fingers, as chewed as possible.
Thanks to everyone who responds to help.

Answer 1

You correctly noticed that there are two options. This is the NS of the domain registrar or hoster. Of course, you need to use the NS server at the domain registrar, because when the hoster is down, you can transfer the domain to another within an hour.
As for mail. You need to set the MX server to "A" record.
That is, you need to register the registrar's mail server with the domain registrar.

Answer 2

mailgun.org
https://www.mandrill.com/

Answer 3

The registrar needs to delegate the domain, for this, Primary and Secondary DNS are prescribed - authoritative DNS servers for this domain. Those. DNS servers that hold the specified domain zone. Those. those servers that host the master and slave zones for this domain, i.e. servers that report the names of this domain to the rest of the Internet, in which the zone records change.
Further, there may be two options:
1. The registrar provides the DNS hosting service free of charge, but upon registration of the name. All changes are made from the recorder panel.
2. The registrar does not provide DNS hosting service and you need to raise either your own DNS server, or buy / look for free DNS hosting.
If on the fingers, then to delegate a domain, it is enough to register authoritative DNS servers. As a rule, the registrar provides DNS hosting service for free, therefore, by default, he registers his servers there and creates a new zone. This happens invisibly to the client. And since If this is his server, then you will have to edit the zones from the same admin panel, where the domain name is contained. This is where beginners get confused.
It is better to ask specific questions with examples, then you will get more specific answers.
And now to the question itself. What does DNS have to do with it?
Mail can not go for a thousand reasons. First, understand the sending mechanism itself. Maybe you don't even need DNS. You do not raise a mail server.
Well, after you understand:
- see the logs
- configure to send via gmail or yandex
- the hoster can cut ports 25\465\587, this is a common practice.