[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 Monarobase):

 Replying to [comment:60 siliconforks]:
 > Replying to [comment:59 Monarobase]:
 > > The reason we consider SPF not to be the concern here is that SPF
 configuration has always been part of email delivery, and most hosting
 providers already handle this today. When domains are hosted with us, SPF
 is preconfigured; when they are not, customers are generally advised to
 copy or adapt existing DNS records. In other words, this change doesn’t
 materially alter the SPF situation.
 >
 > My point is that this change can break SPF on servers where this was
 working before.  I'm still not entirely sure if you're disputing that, or
 if you simply don't consider that a major problem  because it's something
 that can easily be fixed.

 I said SPF was not the issue for us because for a web host it's easy to
 fix for domains that use their DNS servers and also easy to check and warn
 customers who don't use their DNS servers.

 **What's not easy for a web host** is to fix the issue added by WordPress
 6.9 without adding a plugin to customers websites which would require
 their consent and would cause a lot of support requests.

 We have considered  the following solutions to the issue added to
 WordPress 6.9 :

 - Rewriting all wordpress at domain.tld to system_user at server.hostname  : We
 cannot do this because we can't be sure that a customer does not use
 wordpress at domain.tld
 - Installing a mu plugin automaticaly on all WordPress websites to fix
 this issue : We refuse to install plugins without our customer's consent
 so this is complicated to do.
 - Allow our customers to send e-mails with invalid return paths : We don't
 want to risk our IP's from having a poor reputation due to poor hygiene of
 the e-mails that our IP's send.
 - Contacting all of our customers and telling them to install and
 configure a plugin : This will cause a huge amount of support and some
 customers might believe it's not an issue with WordPress and think it's an
 issue with our servers.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64368#comment:61>
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