[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
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 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:49 SirLouen]:
 > From my experience, these hostings tend to add their SPF domains to your
 DNS records as they generally control the registrar.

 Yes, usually I would expect the hosting company to do this.  In fact in
 the case of DreamHost it does add an SPF record by default:

 https://help.dreamhost.com/hc/en-us/articles/216107737-SPF-overview

 So if you're running WordPress 6.9 on a DreamHost server and the default
 DreamHost-created SPF record is present, you should not have any problem.

 However, there's still a lot of things that can potentially go wrong here:

 1. The SPF record is just a DNS record like any other and is editable; so
 it's possible that the user may have changed the SPF record in the past
 and now it no longer works properly.  This would not have been a problem
 in WordPress 6.8 because the SPF record was essentially unused; however,
 now in WordPress 6.9 the SPF record ''will'' be used, so any problems with
 it will surface.

 2. It's possible that some people might be hosting their site on a
 DreamHost server but might have their DNS hosted somewhere else.  In this
 case the SPF record might not even exist.

 3. Another possibility is that there may be some plugin doing something
 bad, like using the admin email address as the "From" address.  This is
 not a new issue - it has been discussed before in
 [https://core.trac.wordpress.org/ticket/60420#comment:11 this ticket].
 However, WordPress 6.9 may have exacerbated the problem, because now if
 there is an invalid "From" address, it will also appear as the envelope
 sender as well.  This seems like it might be the case in
 [https://core.trac.wordpress.org/ticket/64368#comment:5 this report
 above].

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Ticket URL: <https://core.trac.wordpress.org/ticket/64368#comment:50>
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