How to keep different domains and one email for everything?

Question

Domain Name System

There are domains, say, a dozen. On each of them it is necessary to receive and send emails of course.
And I have a main email account, let's say on gmail'e or yandex or fastmail - it doesn't matter.
Question: how can I make it possible to receive and send emails from this one account for each of these domains, as if each had a separate email account?
What do I need to configure, what to prescribe? MX - how exactly? How to create your own emails?
And how then to send mail from my main account, but on behalf of my other domain?
That is, so that it seems to the user that I sent from the domain to which he wrote to me initially. And my main domain should not appear anywhere, if possible.
PS
The domain hosting itself is located on different servers: digital ocean and the like.
And the registrars for domains are also different: one is with the goudyadi, the other is with the name, etc.....
Now I still have different mail accounts for each domain, which is inconvenient.

Answer 1

First, you need to connect pdd.yandex.ru for your domains. Then create one gmail account, on all others set up mail forwarding to this gmail account. And finally, set up accounts from which it will be possible to send letters https://support.google.com/mail/answer/22370?hl=ru.
But personally, I prefer to have an email client like thunderbird

Answer 2

create emails for all domains and forward to the main email

Answer 3

There is a mechanism of mailbox aliases (aliases) that implement forwarding of incoming mail to a specified address without actually creating separate ones. It is regularly supported by all MTAs.