[wp-trac] [WordPress Trac] #64367: Upgrade to WordPress core 6.9 from 6.8.3 causes WooCommerce email failure?

[WordPress Trac]

#64367: Upgrade to WordPress core 6.9 from 6.8.3 causes WooCommerce email failure?
-------------------------------+------------------------
 Reporter:  philipg100         |       Owner:  (none)
     Type:  defect (bug)       |      Status:  closed
 Priority:  normal             |   Milestone:
Component:  Mail               |     Version:  6.9
 Severity:  normal             |  Resolution:  duplicate
 Keywords:  reporter-feedback  |     Focuses:
-------------------------------+------------------------

Comment (by desrosj):

 > Okay implementing the code snippet you suggested has worked.

 Great! Thanks for confirming that. This seems to confirm that you are
 experiencing the same issue as reported on #64368.

 > HOWEVER -I'm not trying to be difficult here but I look after and manage
 upgrades for a significant number of WordPress sites. Am I really now
 expected to now implement this code snippet on EVERY site?

 It's possible a fix in WordPress itself would be made and released in
 6.9.1. But it's also possible that there is a misconfiguration somewhere.
 This snippet was meant as a way for you to help contributors to WordPress
 narrow down and confirm what is actually causing the problem, regardless
 of where the problem is.

 Since the snippet does resolve issue for you, so you are free to use it
 however you would like until the root cause is identified and fixed.

 > Surely email functionality is CORE and crucial to the successful
 operation of a business website? I'm sorry but I find your response to
 this issue a bit on the 'complacent' side. I'm worried that you are now
 NOT going to fix this issue in a later release?

 To be clear, no one has been able to identify exactly what is causing the
 issue. So it's not possible to say whether it will be fixed or not, and
 committing to a specific course of action is premature and irresponsible.
 This issue is being caused by a fix for a valid bug and seems to have
 exposed instances where servers may be misconfigured. But guidance can't
 be given until it's fully understood.

 WordPress has tens of thousands of unit tests in place that run every time
 the code is updated. But those only test the code in isolation, and does
 not cover 100% of the paths in the software. There are also
 [https://make.wordpress.org/hosting/test-results/ hosting tests where
 hosting companies run those tests within their hosting environments and
 report the results to WordPress.org so that issues can be surfaced].

 Leading up to each and every WordPress release, the project also has
 several beta and RC releases. These are announced on [WordPress.org/news
 WordPress.org/news]. The
 [https://make.wordpress.org/core/2025/10/21/wordpress-6-9-beta-1/ beta 1
 release for 6.9 was on October 21st] and marks the beginning of the call
 for testing phase of the release cycle.

 The contributors helping to maintain the software can only test perform so
 much testing. Catching issues like this one depends on hosts, agencies,
 and users testing in staging environments with real websites. Despite 6
 weeks of calls for testing, this issue was not reported prior to 6.9 being
 released.

 > https://www.365i.co.uk/blog/2025/12/02/wordpress-6-9-broke-3-plugins-
 fix/ have a look at this thread-there are also a number of problems
 associated with third-party plugins. I'm not sure what the protocol is
 here-is it down to the plugin developers to make their plugins compatible
 with 6.9?

 I'm not going to comment on these reports because each one seems to be the
 result of a different unique bug.

 The WordPress project and those contributing directly to the open source
 software are not responsible for testing every plugin. In cases where a
 plugin breaks after upgrading, it's often because they were not tested
 against 6.9 far enough in advance or at all. It's the responsibility of
 the companies or individuals responsible for maintaining each plugin and
 theme to test their software against each version of WordPress.

 As for advice how to handle things in the future, I can't really answer
 that for you,. How you handle updating your sites is an individual
 decision that you have to make on a per site basis. Despite every effort
 made and well-meaning intentions, the unavoidable truth is that bugs can
 and do happen in software. Balancing the various risks and how they impact
 your business with staying up to date and the amount of testing to be
 confident in updates is something you need to consider for yourself.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/64367#comment:9>
WordPress Trac <https://core.trac.wordpress.org/>
WordPress publishing platform