Dear friends,
Since today I can not create a message containing an image which I import from

 D:\_NET_INF\Download\Attachments\2023-04-27_09-52-03.png

The 'ready to send' message contains a rectangle of the image size and in top left corner with a red question mark. Hovering over this I see the message "Error 120006 The URL does not use a recognised protocol".
The message is compoled with Rich Text.
The relevant part in the HTML facet reads:

<div align="left" style="min-height: 594pt; "><img src="cid:2209265.1683533827.31039" width="754" height="792" border="0" alt="graphic"/></div>

I do not see where the problem may come from.
Pegasus is v4.8, build 1028 as of 2022-01-16
Windows is
CurrentBuild 19045
OSbuild 10.0.19045.2846
OSdisplay 22H2

I can not duplicate the problem. I have created a path and filename that duplicates your example and have tested on v4.80 and v4.81 beta. I added the image using Insert a picture > Add a picture.

Is the problem occurring with all images?

This is an error usually only seen when opening copies to self. It shouldn't occur when opening queued messages neither in the ready to send nor the final format message being sent. And the above HTML snippet shows no errors.

This is an error usually only seen when opening copies to self. It shouldn't occur when opening queued messages neither in the ready to send nor the final format message being sent. And the above HTML snippet shows no errors.

Thanks, Brian, for Your tests.
I insert the pictures with the very same procedure. The problem is new to me and therefor I added the detailed Windows information.
Yes, it happens with various types of images (tested: png, jpg).
It happens with any source location on my system (J:camera chip, G:, D:...)

Looking into older sent messages with images reveals the following:
In the 'copy to self' folder there are the messages with the empty images (and just a question mark in them).
Sending the messages (to myself works fine for these tests) is possible - in the status line they are listed as queued) - And I receive them correctly with embedded image.

So the problem is only in the 'copy to self' folder which is named !_sendt
I have now tried various names for this folder: 0_sent OutBox - no positive effect. But they were all sent correctly with embedded image...

Yes, Michael, this observion is also true...
So my shattered mind is calmed down now...

It's always been like this, but if you update Pegasus Mail to v4.81 public beta you'll now get the option to save copies to self in the final format so they'll appear exactly as they'll arrive at the recipient's end:

Wow, Michael, this needs to be tried - it would dissolve my annoyance and suspicion....

Have installed the beta version - Wunderful feature!!!

Added 2023-05-17:
And one of the very welcome features is this: prompt windows (e.g. to delete a a folder) now open centered to the main window - not centred to the monitor estate. On a 31" wide monitor this is a real releaf!