Rob thank you for posting this as I did the same thing and without your comments I would still be trying to figure it out duh~!  It was me~! Now I remember dragging it down to read a long list of recipients and copying them and guess I forgot to drag it back up. blush.

In our office on a 4.7 version of Pegasus Mail the message in the e-mails is not showing up; only headers are shown.

Okay, I think I have answered my own question. Just below the top of the e-mail message (where the e-mail addresses and subject line are located) is a line separating this section from the e-mail message. Apparently, someone in the office dragged this line to the bottom of the message thereby obscuring any message. If the cursor is brought down to the bottom of the window it will at some point turn into a vertical double sided arrow. Left click and drag the line back up thereby uncovering the message.