When using the formatter of the Mime Mail module the Content-Type header set by Block Inactive Users cannot be replaced.
The result is that a the Content-Type header in the mail has the value "text/html" instead of the expected value:
multipart/alternative; boundary="b1=_4pEkzMNTCKdwPG4hZRDSOlsO4hvssF1dt1v3MWfpw"
and the mail cannot be displayed correct by mail clients.
Install both modules (Mime Mail and Block Inactive Users), and set the use of the MimeMail formatter.
It can be debated which module is to blame, but I propose the easier fix in the Block Inactive Users module by changing the line 207 in the InactiveUsersHandler.php form:
'content-type' => 'text/html',
into:
'Content-Type' => 'text/html',
This is the correct notation for Content-Type, and it will allow the array_merge in MimeMail.php on line 205 to work as expected.
Fixed
2.5
Code
Created an MR with your suggested solution. Thanks for raising this.
Automatically closed - issue fixed for 2 weeks with no activity.