EHLO Problem and Solved

Situation:

A website (www.mysite.com) is hosted on a site other than the one of your mail server (mail.mysite.com).

The website responds to both the mysite.com and https://www.mysite.com addresses

The Easy WP SMTP user correctly configures the options for the SMTP dialog.

Problem:

When the plugin generates the mail result of a form, the mail server on mysite.com it rejects it at the time of sending the EHLO command, with a similar message
to this:

2021-04-21 17:11:25 H=(mysite.com) [xx.xx.xx.xx] rejected EHLO or HELO mysite.com: No you are not ME or OURS (HELO was [mysite.com] and equal my local domains or my domains relay)

Cause of error:

When the plugin generates the mail result of a form, it makes use of the library PHPMailer. This library establishes a series of default values, which are used for the vast majority of cases. One of them is the value of $Ehlo variable. If this value is empty, the library takes the value of $Hostname variable. If this value is empty, it takes it from the name of the server where it is running.

As it turns out the site is set to mysite.com, that’s the name you use with the EHLO command. And when the mail arrives at the mail server, it rejects it because it does not support emails from machines other than his own (with the same name).

Immediate solutions (one of these):

1- Change the name of the web server to https://www.mysite.com, so that this is the value that PHPMailer take. This solution will not work if the reverse resolution of https://www.mysite.com is not correct (case of mail servers that check the direct AND inverse resolution names of incoming connections). For example, https://www.mysite.com resolve to xx.xx.xx.xx, and the inverse resolution of this IP are dns9198.phdns17.info, so the email is rejected.

2- Configure the mail server so that it directly admits external emails from mysite.com (this solution is a bit dangerous). If it can be restricted to the IP of https://www.mysite.com, perfect.

3- Edit the PHPMailer.php file to change the line

public $Helo = ”;

or the line

public $Hostname = ”;

to indicate the name (*NOT IP*) of the server that hosts https://www.mysite.com (for example, dns9198.phdns17.info). This solution is *not* maintainable – it will be lost in the next library update.

Ideal solution:

Since PHPMailer does not consider the case of reading the default SMTP configuration from an external file, nor from the global variables of WordPress, the plugin should allow editing the value of Ehlo or Hostname, taking the first default value the name of the web server where it is running or take it from the name of the mail server that is being indicated. Most users would not need fill in this field, so it should be filled in automatically, ideally in the time to show the plugin for the first time.

JF