How does an SMTP server communicate with a mail service?

Question

Mail server

We use the Unisender service for commercial mailings. The domain mail itself is located on Yandex (SDA).

I am writing my own e-mail mailer: in my program, I connect to the Yandex smtp server and can send mail from our domain to user groups without any problems.
However, I ran into another difficulty: unisender somehow receives data that some subscriber has unsubscribed (I understand how this works), or added a mailing to spam (I don’t understand how this works). It turns out that the Yandex mail server, after sending the letter, receives a response from the mail client and sends data about those who added the mailing list to spam to unisender. I don't understand how he sends this data and where to get it from.

What exactly are the mechanisms that allow the abstract unisender (or any other mailing list service) to know that the user has added the mailing list to spam?

Answer 1

Good afternoon!
in my program, I connect to the Yandex smtp server and can send mail from our domain to user groups without any problems.
In fact, Yandex robots have recently often blocked mailings via their SMTP, if you want it to work reliably, it’s better to use third
-party unisender somehow receives data that some subscriber has unsubscribed
here everything is simple, following the link in the letter
or adding mailing to spam
, the Unisender puts its return address in the MAIL FROM field and receives complaints about spam through the FBL tools. When sending using your method, you need to set the rua parameter in DMARC and set up postmasters (for example, mail ru does not take mail from DMARC, for them you need to register it in the postmaster, but gmail and yahoo take it).
It turns out that the Yandex mail server, after sending the letter, receives a response from the mail client and sends data about those who added the mailing list to spam to unisender.
Yandex does not participate in this operation at all, letters are sent from the unisender servers and all abuse reports and bounce are sent directly to the unisender servers due to the fact that mail from is specified by them and not yours

Answer 2

it?