Why delegate a domain to Yandex when setting up Yandex.Mail?

Question

Mail server

I set up "mail for the domain" with Yandex, add the domain, and right there at the beginning of the instructions, Yandex writes:

Делегируйте ваш домен на Яндекс
Измените NS-сервера вашего домена (эта процедура производится при помощи инструментов регистратора доменов или хостинг-провайдера, у которого вы приобретали домен):
Первичный DNS-сервер: <b>dns1.yandex.net</b>
Вторичный DNS-сервер: <b>dns2.yandex.net</b>

I would like to clarify why this is necessary?
Will Yandex.mail work without this? Why should I delegate a domain to them if I don't want to?
And are there any benefits if I do this? And why does Yandex need it at all? After all, this is a waste of resources 0_o

Answer 1

To begin with, you should read how mail and mail servers work.
For work in general, it is not necessary to delegate a domain to them, if you yourself write everything you need in the settings of the dns zone. Convenience of domain delegation to Yandex - protection from changes within Yandex itself, wherever it transfers your domain, on which Yandex server it is not spinning, Yandex DNS will send it to the right place.
If you don't want to delegate a domain - don't do it)))