How to configure SMTP session logging?

Question

Mail server

Some of the letters sent from the site do not reach mail.ru mailboxes. How to enable logging of the SMTP session of sending emails? We need to see what the mail.ru servers respond to when trying to send letters.
The mail.ru support service asks: "...send the full log of the SMTP session of sending a letter to the mail.ru address. The specified log should contain several attempts to send letters to the mailboxes of our post service, as well as the full response of our emx.mail server. en..."

Answer 1

logs of the mail server from which letters leave are necessary. If you do not have such logs, then it is almost impossible to understand the reasons

Answer 2

Need details. The mind-reading machine is under development in China
. Do you use Outlook? or sendmail, postfix. any one?

Answer 3

For starters, I'm not an expert in php, I don't know the details of how this function works. question - the function itself connects to a remote server and sends mail to it or it uses the system mailer on the current server (where the site itself is located).
if the second - then study the logs, it will be something like /var/log/maillog or /var/log/mail.log , depending on the system.