[wp-trac] [WordPress Trac] #37787: WordPress MU 4.5.3 password reset mail doet not work. Other mail does.

[WordPress Trac]

#37787: WordPress MU 4.5.3 password reset mail doet not work. Other mail does.
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 Reporter:  BjornW        |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Mail          |    Version:  4.5.3
 Severity:  normal        |   Keywords:
  Focuses:  multisite     |
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 I'm using a 4.5.3 WordPress MU installation.

 Using the password forgotten functionality on the wp-login.php page I get
 the following error message:

 ''The e-mail could not be sent.
 Possible reason: your host may have disabled the mail() function...''

 '''The weird thing is, if I add a new user it will send this email without
 any issues at all.'''

 I've removed all plugins from the plugins folder, and all themes except
 for Twentysixteen, after that I've checked the following:

 - Made sure mail works by logging (via ssh) into the server an sending an
 email with sendmail commmand line application. Mail was sent and received
 without any issues.

 - Sent mail using a PHP script using mail() on the commandline with php
 -f. Mail is send & received, works as expected.

 - Made a tiny plugin, hooks into init and sends email with PHP's mail().
 Mail is sent & received, works as expected.

 - Changed the tiny plugin to use WordPress' wp_mail() function. This fails
 silently, even when hooking into wp_mail_failed.

 Configuration:
 - WordPress Mu 4.5.3
 - Nginx with php5-fpm
 - Server uses sSMTP connecting to another mail server.

 '''Conclusion'''
 So far it seems that something is making wp_mail() fail silently when
 calling it directly from a plugin or when using it for a password reset
 while sending out an email to a new uses works.

 Any tips on debugging is much appreciated!

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Ticket URL: <https://core.trac.wordpress.org/ticket/37787>
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