[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:                |     Focuses:
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Comment (by zoe20):

 Hello,

 After updating my WooCommerce site to WordPress 6.9, all WooCommerce
 store-related emails stopped sending (such as New Order, Processing Order,
 and other transactional emails).

 However, PayPal payment confirmation emails continue to arrive without any
 issues, so the problem seems isolated to WordPress/WooCommerce-triggered
 emails.

 When I downgrade back to WordPress 6.8.3, everything works perfectly
 again.
 No other configuration changes were needed — simply reverting WordPress
 itself restores full email functionality.

 This confirms that the issue is directly related to the WordPress 6.9
 update.

 I also see this has been documented here:
 https://core.trac.wordpress.org/ticket/64368


 —which appears to match the behavior I'm experiencing.

 Could you please clarify:

 When is WordPress 6.9.1 expected to be released?

 Is there any temporary workaround or patch available that resolves this
 issue while staying on WP 6.9?

 Thank you — happy to provide additional details or logs if needed.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64368#comment:32>
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