[wp-trac] [WordPress Trac] #15448: wp_mail() sets Content-Type header twice for multipart emails

[WordPress Trac]

#15448: wp_mail() sets Content-Type header twice for multipart emails
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 Reporter:  rmccue                               |       Owner:  nacin
     Type:  enhancement                          |      Status:  reviewing
 Priority:  normal                               |   Milestone:  Future
Component:  Mail                                 |  Release
 Severity:  normal                               |     Version:
 Keywords:  gci has-patch westi-likes needs-     |  Resolution:
  refresh                                        |     Focuses:
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Comment (by christinecooper):

 Just to highlight that sending multipart emails (html/text) with wp_mail()
 (to reduce chance of emails ending up in spam folders) will ''ironically''
 result with your domain being blocked by Hotmail (and other Microsoft
 emails).

 We are currently discussing this severe issue over at WPSE:

 [http://wordpress.stackexchange.com/questions/191923/sending-multipart-
 text-html-emails-via-wp-mail-will-likely-get-your-domain-b]

 This issue has been pending for 5 years and it hasn't appeared as if there
 is any interest to implement a fix to core. Maybe it is about that time to
 invest and resolve this properly.

 The patch posted above 15448_June2015.diff​ works.

 Consider implementing this solution.

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Ticket URL: <https://core.trac.wordpress.org/ticket/15448#comment:31>
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