How is mail sent from the IP address to the desired domain?

Question

Email

Hello, as I understand this process: my mail client accesses the dns server, it gives out the IP address, the client connects, sends data, everything seems to be simple. But after reading in reliable sources https://ru.wikipedia.org/wiki/%D0%AD%D0%BB%D0%B5%D... about the process of mail forwarding, some kind of relays and client-servers , what the hell? Why is all this necessary? I understand spammers!, from my mail agent the most spam, with its moronic projects. Is it all simple?

Answer 1

If sending is from an email client, in short, the process looks like this (let's take, for example, mail to mail ru and the recipient's mail [email protected]):
1. the client sends a letter to the mail ru
server 2. the mail ru server sends a request to the DNS zone of the krutayafirma domain .com, find out the mail servers of this domain (MX records)
3. From the MX records, the record with the lowest priority is selected and the server makes a request there - [email protected] - is there such a box?
4. If the server does not respond, the next highest priority MX record is taken and the request is repeated
5. If the recipient's server says yes, the message is sent there
6. The recipient's server's spam filters analyze the message and decide whether to send it to the inbox, to the spam folder, or in general kick back

Answer 2

I won’t risk describing all the stages of sending a letter, but I’ll pay attention to a couple of points.
First, email technology has historically not provided any kind of authentication when sending emails. Imagine a post office with an outgoing mailbox. You can come to the office and put an envelope in the box, indicating any name in the “from whom” field - postal workers will not check whether you indicated your name or introduced yourself as someone else.
Many SMTP servers operate in open relay mode by default: they accept outgoing messages from any users (including anonymous ones who did not enter a login and password) and try to deliver them to recipients. Major mail services (Gmail, etc.) close this option, because a lot of spam from one server spoils the reputation of its IP addresses and leads to the fact that other letters from these IPs will be marked as spam.
Secondly, mail servers can have processing rules for both incoming and outgoing messages. This may be required for various reasons: to filter out spam before it leaves the server and ruins its reputation, to prevent the leakage of corporate data, to archive all employee correspondence (see eDiscovery), etc.

Answer 3

relays and client-servers,

Not all mail servers sit directly on the Internet. There may be intermediate gateways, for example, in companies where there is a mail relay outside, which receives external mail via SMTP, possibly filters, forwards it to the internal exchange via SMTP intranet, which already distributes it to its Outlook via imap.

Why is all this necessary?

because the global Internet is a little more than 10 computers in a local area and is much more complicated.
Because mail traffic can be so large that one machine does not physically have time to process it, and it is distributed over a pool of machines.