wp_mail fails to send email on WP auto update when wp-cron is called directly by php

[pessoft]

Hi!

On some of our WordPress instances wp-cron.php is called by system cron directly as a parameter to php command ( not via HTTP request ). This is partially to make sure that WP cron is executed regularly and partially to make sure that all tasks in cron will not hit a timeout for HTTP communication on servers and reverse proxies.

In a case when WP triggers auto update during such php execution and wants to send email about success, there is no $_SERVER['SERVER_NAME'] available and no From: header passed to wp_mail, therefore sender's email is not fully generated and delivery fails:

PHP Fatal error:  Uncaught exception 'phpmailerException' with message 'Invalid address:  (setFrom) wordpress@'

There are at least three possible solutions which could generate valid email address and maybe help in more scenarios too:

1) WP auto update fix
As WP update knows what is the site URL of WP during update, it could construct sender's email directly from configuration, pass it as From: header to wp_mail and not need to rely on whether SERVER_NAME is set or not.

2) Local hostname fix
When wp_mail is called and From: header is not present, wp_mail tries to construct the sender's email from SERVER_NAME. In case neither SERVER_NAME is available, wp_mail could try to call function like php_uname or gethostname yet as a last resort for construction of sender's email. This could ( at least to some extent ) help with such wp_mail calls where SERVER_NAME is not available.

3) Sender's email configuration option
By providing possibility to have a default sender's email for WP configured, it would be possible to use such address as sender in wp_mail function and rely on SERVER_NAME only if configuration option would be not set ( or set empty ). Based on history of tickets related to sender's email address, this fix would help many users for which current construction of sender's address is not suitable and work also in backward compatible way.

Do you see any of these options acceptable?

Thanks.

[chesio]

I can confirm the issue, I have the same problem on one webhost that runs WP Cron via PHP CLI. Also, because of this issue, debug.log gets populated with Undefined index: SERVER_NAME notices.

[pessoft]

Use hostname if SERVER_NAME is not available for default sender of wp_mail function

[pessoft]

Unittest to verify that phpmailer instance From field is updated by wp_cron

[pessoft]

I've added unit test to verify that when wp_cron has been called, that also From parameter of PHPMailer instance has been updated from its initial state. This update does not occur in cases when SERVER_NAME is not available and results in WP error messages and emails not being sent. This unit test is depending on #41485 as MockPHPMailer is not correctly reset and From parameter cannot be tested for changes from initial state.

[SergeyBiryukov]

Related: #25239

[Mte90]

I confirm this issue, I have plugin that use wp-cron to send emails but in our installation we are using cron by the system.
I am applied that patch but looking at the code will probably fix the issue.
In our case we had a lot of email errors, this can explain our problems on communication.

[Mte90]

Applied the patch and no anymore errors on my WordPress!
It is possible to move this on 4.9.5?

[Mte90]

refreshed and merged

[Mte90]

Patch refreshed and merged in one diff file.
I hope to will be integrated in the next version because is very boring do a manual patch to wordpress installation.

[afercia]

40810.diff​ needs some coding standards.

[Mte90]

fixed coding standards

[Mte90]

Refreshed for fix coding standards :-)

[brambo123]

There are more options than just $_SERVER['SERVER_NAME'] and php_uname().
The functions get_site_url() and get_home_url() are also very suitable.

In addition, there are more prefixes than www., for example: staging. and dev.
By using getmxrr() it is possible to find out if the domain name is valid to send mail from.

[brambo123]

Use more possibilities to find a domain name and use getmxrr function to find valid email domain name

[pento]

Patches need review and testing.

[audrasjb]

Hi,

With 5.4 Beta 3 approaching and the Beta period reserved for bugs introduced during the cycle, this is being moved to Future Release. If any maintainer or committer feels this should be included or wishes to assume ownership during a specific cycle, feel free to update the milestone accordingly.

[enrico.sorcinelli]

It looks like a bug that should at least be fixed in 5.5 (even in a possible 5.4.x maintenance release)

[Mte90]

This problem is related to this one in multisite that has a patch too #47733

[francina]

With auto updates from plugins and themes being merged in 5.5 and Core auto-updates in 5.6, this seems like a ticket worth revisiting.

It looks like it needs a few things to be ready for 5.5:

• Refresh the patch
• Write the unit test
• Bring it up to one of the planned bug scrubs

In short, it needs a champion ;-) But it also needs some direction from the Mail components.
In any case, pinging @SergeyBiryukov for evaluation of the ticket.

Thanks!

[ocean90]

Closing as a duplicate of #25239 to keep the discussion in one place and since this doesn't only affect wp-cron.