[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:  needs-patch   |     Focuses:
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Changes (by jorbin):

 * keywords:  has-patch close => needs-patch


Comment:

 > It's complicated to test this

 I'm specificly thinking about testing on affected systems rather than
 trying to create labratory conditions.

 Because this is a regression that can fully break outbound email, that
 damaged IP reputation can hurt not just one site or application, and that
 reverting it (or downgrading to 6.8.3) has successfully solved the issue
 for every reporter, I think that the safest route for 6.9.1 is to revert
 [61010] rather than upgrade phpmailer. This doesn't need to preclude work
 in 7.0 that builds upon this attemmpt and tries to find new ways to ensure
 emails are successfully delivered.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64368#comment:78>
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