Thanks @[deleted], I wish I'd spotted that before - I was up til the small hours last night doing a similar patch :)The problem is caused by the fact that mail fetcher skips the attached message because it has no name (understandably), so ends up skipping the attachment altogether. If the attachment has a named attachment in itself, like an image, the structure walk finds that and notes its name and mime type. Unfortunately, when it comes to add the body content, it then finds the content of your attached message. So you end up with an attachment called maybe image001.png, type image/png, but the content of it is "<html>... your attached message ... </html>". All a bit screwy.The solution is to treat the rfc822 attachment as a first class citizen regardless of being unnamed, not recurse, and give it a name with a .eml extension. Then it adds the attachment which you can click on and it should open in your mail client, certainly works with Outlook.