From OE 'Help'
To combine multipart messages-

Sometimes, when a large message (one that contains pictures, audio files, or other large objects) is sent in e-mail or posted to a newsgroup, it is broken into smaller files and displayed as several messages. You can combine the messages to recreate the original message and display it in Outlook Express.

Select all of the messages that are part of the original message (each part will usually have a number).
On the Message menu, click Combine and Decode.
If needed, reorder the parts in the correct sequence.

Note
After you combine and decode the message, it is displayed in a separate window. The message will continue to be displayed in the message list as several smaller messages. To save the recreated message, on the File menu, click Save As.

Hope this helps.
I finally got a newsreader, and from looking at the headers, those that see the pix are using them too (some are free!). Click attach file and send. (not broken and sent)
I think he may be including the binary code in the text of the message instead of just attaching the image itself to the message.
Nope - simple attachment
I think the yEnc, which is a form of coding, is part of the clue.
Nope. yEnc doesn't split files; it is simply a more efficient way of encoding the characters. Characters exist now that were not there in the days of radioteletype. Encoding each one of them required multiple characters to be sent. yEnc sends one character.
HOWEVER-- It IS possible that OE still doesn't support yEnc, though dozens of plug-ins exist for it.
Google is your friend.