This question may be related to a resolved thread.
The original question in the above thread wasn’t finalized and it’s the same one I’m having.
1) Admin -> Email Configuration has HTML set as Default Mail Format
2) PHP Mail is set
I used the email_test.php script and the formatting is retained in the test email generated from that. But the password recovery email the formatting is stripped and is a jumbled mess - as described in that original post.
EE 2.3.1