Using an external Mailserver

[hadiaj168]

hi!
i want to use an external Mailserver and read this .
i change name to my external server ip and deselect "Local Mail Server".
then i create a user with same domain name on mailserver an create a mail Accounts .
but when i send a email from my main server with another domain (and user)

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  [email protected]
    all relevant MX records point to non-existent hosts

------ This is a copy of the message, including all the headers. ------

Return-path: <[email protected]>
Received: from localhost ([127.0.0.1] helo=[mainip])
	by mail.domain.ir with esmtpa (Exim 4.76)
	(envelope-from <[email protected]>)....

whats my wrong?
excuse me for my bad english!

 

[Richard G]

all relevant MX records point to non-existent hosts

That is the error notice, so it seems the mailserver where you pointed your MX records to, has no A records so it isn't recognized.
A mailserver has to have an MX and an A record.
I think you will be fine if you provide your external mailserver with an A record. So it needs a hostname where you can point the A record to.