PMail does not seem to be able to forward an email which only has an HTML part but no text part. Some mail systems show the forwarded message as raw. GMail actually rejects the message as not being RFC5322 compliant.

PMail treats both "forwarded" mail and "bounced" mail in the same way and I get the same errors.

PMail is able to display the original HTML email but if I forward that email to myself, PMail displays it as raw data.

If I forward the HTML email as a attachment, PMail displays it correctly.

I've seen some posts about this on the Usenet group (some going back to 2003) but they never clearly say anything definitive.

Is this a known issue and is there a workaround?

Windows 11
Pegasus Mail 4.91.1746
IE Renderer 2.7.3.5

One thing we know is that it is best to attach a message if you want the sender to receive exactly what you received but a forward with edit should work.

That said, I was able to successfully forward two HTML-only messages to one of my gmail accounts. Both were forwards with edit. I didn't bother testing bounces because it is rare for a bounce to work anymore due to the anti-spam efforts of matching the From: header with the sending address. The question now becomes what am I doing differently.

This is an image of the forward setting I used in one of my tests. My other test was the same except the "Forward any attachments..." option was unticked.

When sending as an attachment, confirm this setting it ticked.

FWIW, I confirmed that my test messages displayed fine in both Pegasus Mail and on the Gmail web interface. Don't know what other email clients might do.