SMTP verification error

[ribvid]

Version

1.0.3

What did you expect to happen?

I installed the Acorn Mail package, configured my SMTP authentication data in .env, and tried to send an email using WP-CLI. I expected the email to send successfully without any errors.

What actually happens?

Emails fail to send and I get this SMTP error:

SMTP Error: The following recipients failed: [MY EMAIL] Verification failed for <wordpress@[MY DOMAIN].test>
  The mail server does not recognize wordpress@[MY DOMAIN].test as a valid sender.
  Sender verify failed

The only way I can get emails to work is by manually adding this code:

add_filter('phpmailer_init', function ($mail) {
    $mail->Sender = $mail->From;
    return $mail;
});

Steps to reproduce

1. Install Roots/Sage theme with Acorn
2. Install Acorn Mail plugin
3. Configure SMTP settings in .env
4. Try to send a test email using wp acorn mail:test
5. Email fails with SMTP sender verification error

System info

No response

Log output

Please confirm this isn't a support request.

No

[ribvid]

I think I've identified the cause of this issue. It's related to a recent change in WordPress core.

[Until recently] WordPress has been calling $phpmailer->setFrom() with a false value for an attribute telling it to set the sender address for each message.
/.../
In this patch the flag is being removed, which has the effect of letting $phpmailer set the Sender value, which it does by default using the domain “where the front end is accessible”

When Acorn Mail's phpmailer_init filter runs and calls

$mail->setFrom(
    $this->fromAddress(),
    $this->fromName()
);

The Sender header has already been set by WordPress core.

I'll open a PR with the proposed fix shortly.