[wp-trac] [WordPress Trac] #64368: `Could not instantiate mail function` errors sending mail in 6.9

[WordPress Trac]

#64368: `Could not instantiate mail function` errors sending mail in 6.9
--------------------------+-----------------------
 Reporter:  desrosj       |       Owner:  SirLouen
     Type:  defect (bug)  |      Status:  accepted
 Priority:  normal        |   Milestone:  6.9.1
Component:  Mail          |     Version:  6.9
 Severity:  normal        |  Resolution:
 Keywords:  has-patch     |     Focuses:
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Comment (by siliconforks):

 Replying to [comment:47 dmsnell]:
 > Maybe you are saying that WordPress did not send anything through
 `PHPMailer` in the //before// case, and PHP’s `mail()` auto-set it? and
 somehow that would be some default that hosts configure in a way that it
 would be valid?

 A real-world example might be helpful here...

 [https://core.trac.wordpress.org/ticket/64387#comment:2 This user]
 mentioned using DreamHost for hosting; curious, I did some testing on a
 shared DreamHost server to see how they handle mail.

 If you send email from a shared DreamHost server without specifying an
 envelope sender, it seems that your envelope sender ends up looking
 something like this:

 {{{
 user at pdx1-shared-a2-09.dreamhost.com
 }}}

 Is that address "valid"?  I would say, not really (I'm pretty sure that
 it's not a real mailbox).  However: it is valid in the sense that it does
 pass SPF.

 {{{
 Received-SPF: pass (... domain of
  pdx1-shared-a2-09.dreamhost.com designates 69.163.136.89 as permitted
 sender)
  client-ip=69.163.136.89; envelope-
 from=...pdx1-shared-a2-09.dreamhost.com;
  helo=pdx1-shared-relay-02.dreamhost.com;
 }}}

 So if you have a website `example.com` running WordPress 6.8 hosted on a
 DreamHost server, and you send email, your message will have an envelope
 sender value of something like `user at pdx1-shared-a2-09.dreamhost.com`,
 which is not exactly ideal, but it will pass SPF.

 If you upgrade to WordPress 6.9 and send mail, your message will now have
 an envelope sender of `wordpress at example.com`.  This seems like an
 improvement, but will it pass SPF?  If you have an SPF record for
 `example.com`, and it designates your DreamHost server as an allowed
 sender, then you should be fine - it should still pass SPF as before.  But
 if you don't have an SPF record for `example.com`, or it's incorrect
 somehow, then your message will no longer pass SPF.  So it's possible that
 you may end up having problems getting email delivered (while it was
 working before in version 6.8).

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/64368#comment:48>
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