Rated 4 out of 5 stars

Great add-on. It helped me repair a message that wrongly displayed embedded images at the bottom of the email instead of them being displayed inline in the HTML.

Not sure how it happened, but this add-on allowed me to change easily the email source to fix it.

(In case someone has the same problem as me, more specifically, I changed with it the "Content-Type: multipart/mixed;" in the email source to "Content-Type: multipart/related;". This repaired the email and allowed images to display inline again).

Great tool. I'm sure it will prove very useful for many other things in the future.

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Warning : I may be a bit stupid but it took me some time to use it. I had read the warning on the add-on page about the menu being displayed only in the message pane. And without thinking much, I stupidly thought it meant having an email opened in a new tab.

(i display emails in new tabs by default, not in the message pane below the email folder list).

It does not.

So make sure to open the message pane by pressing F8 first, then right-click in the body of the email in the message page, and you will see the "Header Tools" contextual menu there.