Mimemail + SMTP + Mail System: inline images make body empty
Further investigations lost me into the SMTP Authentication Support module
It's complicated enough and I couldn't locate something to help me find what was the problem coming form my configuration.

After a quick search within issues of Mime mail, someone was linking to another module to handle SMTP connection: enter link description here

Basically it works the same way than SMTP Authentication support but its benefit is you don't have to create a bridge mail system class between it and Mime mail, it's natively integrating with Mime mail.

To make it work properly, I had to configure Mail system as such :


Site-wide default MailSystemInterface class: MimeMailSystem
Mime Mail module class: MimeMailSystem
PHPMailer module class: DrupalPHPMailer


and in Mime mail settings :
 - set Mail engine to PHPmailer