[quote user="Thomas R. Stephenson"]

Right click on the message in the folder listing and select properties.  Make sure that the message is not marked read-only.

[/quote]

That was it.  But I wonder how it got that way.  I have never used "read-only" and I don't believe I ever right-clicked on that message.  Does "read-only" ever get set spontaneously?
 

(PM 4.41) I just received an email ... routine office stuff.  I read it.  I can't delete or move it from the new mail folder.  Simply, nothing happens when I try.  I restarted Pegasus Mail; that didn't help.  I can still read it.  Any suggestions?  Thanks.

Right click on the message in the folder listing and select properties.  Make sure that the message is not marked read-only.