How does the phpmail function work?

Question

PHP

I want to understand how the phpmail function works. You need to understand the full chain. She after all does not use SMTP.

Answer 1

It calls the program specified in the sendmail_path directive with the parameters specified there, and sends it the generated letter with text and headers.
Those. its operation requires some kind of mail server that provides a similar interface, and will deliver the message, from exim or postfix, to the simplest msmtp.

Answer 2

What is incomprehensible?
SMTP is a protocol. Used to send from third-party services with
mail() authorization - php. Built-in function for sending email
sendmail is a mail server.

Answer 3

sending mail using the "php method" is not a good way, because your mail goes through all the filters and provider's servers and there is a high probability of letter loss / non-delivery (especially for small providers)
the most "correct" way for today is to send through a large postal service ( Yandex, mail, google), and they, in turn, deliver mail via secure SMTP directly from your php script.