Upgrade to WordPress core 6.9 from 6.8.3 causes WooCommerce email failure?

[philipg100]

We use a staging site and regularly test WordPresss core upgrades and plugin upgrades before implementing them in the live environment. We upgraded WP Core 6.8.3>>>6.9 and also Woocommerce 10.3.4>>10.3.6. When we did some test purchases we noticed that email notifications from Woocommerce to site admin were no longer working. In order to narrow down what was causing the issue we rolled back the staging site to 'pre- upgrade' and did some test purchases and the emails worked again. We then upgraded JUST WordPress Core and tested again and found that email notifications no longer worked. Is there something that has happened maybe to PHP mailer?

[jonsurrell]

There's some conversation about an issue with email in 6.9 in ticket #49687.

[siliconforks]

Replying to philipg100:

When we did some test purchases we noticed that email notifications from Woocommerce to site admin were no longer working.

When WordPress tries to send email here, does it fail with some error message? Or does it appear to work without errors, but then the email simply never shows up in your inbox?

You may want to try using the ​Health Check & Troubleshooting plugin - it has a tool for sending email and (sometimes) diagnosing errors.

[desrosj]

I've opened #64368 for tracking the issues related to #49687 for the 6.9.1 release so that any required changes can be made.

In order to keep all related conversation in one place, I am going to close this out as a duplicate of that one.

@philipg100 if you are able to provide more details about the issues you are seeing and it ends up being completely different than #64368, this can be reopened with more context. I'm also marking with reporter-feedback in the mean time, which indicates more details have been requested from the person who created the ticket.

[philipg100]

@desrosj as far as I can tell there are no error messages -the emails simply don't show up in the inbox.
I looked at the subreddit posts on the subject and they suggest using an SMPT plugin to resolve the issue -I have known this plugin to be used on some sites/ hosting environment when the normal wp mail doesn't work. Should I go ahead and try to install this plugin or is the issue going to be fixed in , say 6.9.1? I must say I'm surprised that such an integral feature has been changed since it might potentially affect literally millions of sites?

[desrosj]

I must say I'm surprised that such an integral feature has been changed since it might potentially affect literally millions of sites?

Every change is given careful consideration and only made if multiple contributors are confident in the update. In this case, several contributors with deep knowledge with email felt that the change was solid and low risk.

While it's possible some people have not yet noticed, the number of reports for this issue so far is quite low (less than half a dozen that I've seen). At the scale of WordPress, that is not yet indicative of a major issue.

as far as I can tell there are no error messages -the emails simply don't show up in the inbox.

There's few additional things things to try here. First, could you confirm the WP_DEBUG and WP_DEBUG_LOG are set to true? Also, setting WP_DEBUG_DISPLAY to false will prevent any issues where something fails due to text being output during requests unexpectedly.

After confirming this and checking the logs again, if you're comfortable doing so could you try the following snippet in your theme's functions.php file, or in an mu-plugin file:

<?php
add_action( 'phpmailer_init', static function ( $phpmailer ) {
        $phpmailer->Sender = '';
} );

[philipg100]

Okay implementing the code snippet you suggested has worked. 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?. You say: "While it's possible some people have not yet noticed, the number of reports for this issue so far is quite low (less than half a dozen that I've seen)." That's the problem-people DON'T generally notice emails not working until their business falls through the floor and they start asking themselves: "why aren't I getting any more enquiries or leads? " 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? Can you now give me some direction on what I should now be doing and the steps I should now be taking regarding upgrading WordPress core on my clients' sites? Should I wait for 6.9.1? or are you even going to fix this problem ?

​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? Please can you at least give me some suggestion as to how I should move forward with this
Kind Regards
Phil

[siliconforks]

Replying to philipg100:

Okay implementing the code snippet you suggested has worked. 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?. You say: "While it's possible some people have not yet noticed, the number of reports for this issue so far is quite low (less than half a dozen that I've seen)." That's the problem-people DON'T generally notice emails not working until their business falls through the floor and they start asking themselves: "why aren't I getting any more enquiries or leads? " Surely email functionality is CORE and crucial to the successful operation of a business website?

To be honest, sending email from a web server, in 2025, is unlikely to be very reliable. You need to have about a dozen things configured correctly, and even if you manage to do that, emails still sometimes end up in people's spam folders (or even worse - disappear entirely) for reasons which are not always clear. This is a problem which is by no means limited to WordPress.

Many WordPress administrators attempt to improve email deliverability by installing plugins which do not attempt to send email directly from the web server - instead they will send email via SMTP or via a third-party transactional email service. If email functionality is critical for your website, it may be best to use one of those.

[jorbin]

is it down to the plugin developers to make their plugins compatible with 6.9?

Yes. The expectation is that plugin developers test and ensure their code works with each version. If they believe they have found a bug, they should report it here. Everyone with a plugin hosted in the WordPress plugin repository recieves an email reminding them of this and highlighting changes. There is also a ​field guide published each release with most of the large changes. For example, you can read about the ​email changes in 6.9, which may be causing your issue.

The goal is for things to just work for everyone, but due to the infinite combinations of server configurations, it isn't possible for the volunteer contributors to test them all. That's why there are many calls for testing throughout the release cycle. For WordPress 6.9, there were ​5 different calls for testing on WordPress.org/news (3 Release Candidates and 2 betas).

Thank you for joining in and trying to help debug this so that WordPress can be better for everyone. I would encourage you to share more about your specific server configuration and what your debugging finds on #64368.

[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 ​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 ​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.

[SirLouen]

@philipg100 please check #64368

It's not directly related to WordPress itself, but WP incorporates the library that is causing this conflict. In 6.9 there was a new improvement that "enabled" this bug in PHPMailer. The problem is that this issue was not covered in the PHPMailer tests, so basically it completely flew below our testing radars.

If the fix that @desrosj provided works for you, this will be fixed by the next release, and you will be able to remove that temporary fix.