Hello @li-an,
PHPMailer is the library WordPress itself uses to talk to an SMTP server. It ships with WordPress core, and every plugin that sends through SMTP hands the message to it rather than reimplementing the protocol. PHPMailer then adds an X-Mailer header naming itself and its version, because that is its default behaviour. That is why you see it in most SMTP plugins you test, and why you see it here too even though the mail goes out through your own webhost’s server. Nothing about your host or your credentials is being exposed, it is only the library announcing itself.
WordPress does this on its own as well. A site with no SMTP plugin at all, sending through the standard PHP mail function, produces the same header 😊
That said, I agree there is no good reason for your site to tell recipients which library sent its mail, so I have removed it. From the next version (0.1.7), Meow Mailer sends no X-Mailer header at all when you use SMTP. The header simply will not be there.
One detail in case you compare providers later. The header only ever appeared on the SMTP and Gmail connections, because those are the two that go through PHPMailer. The API based providers such as Brevo, Mailgun or Postmark build the message themselves and never added it.
Thanks for testing carefully and for taking the time to report it.
Cheers,
Jordy.
Thread Starter
Li-An
(@li-an)
Thanks for your explanations. I was surprised because WP SMTP adds SMTP in the header and I thought it was the normal behavior. I understand now that it’s a custom header, managed by the plugin itself.
I supposed that the X-Mailer information could be used by provider to check eventual spam. It’s the reason I was worried about this.
