Posting directly to Web gallery using BES account?

This is a bit odd...

I have a few .Mac web galleries as well as one on flickr. If I email photos there from my BB using (BES) Exchange, it gets returned with:

The message cannot be delivered due to a configuration error on the server. Please contact your Administrator

Why would the BES server reject it?

Yet, sent from my desktop... it works. Initially, I thought it was a .Mac issue because it allowed me to send it via the BB, using my .Mac email account and the image posted fine. I ruled out that either web gallery is "looking" at the "from" address.

Then I tried my Flickr account, same issue. Allows postings from the BB, IF I send using my .Mac account and rejects messages sent through the BES.

From the desktop, either account works fine.

To further Clarify:
Take Picture on BB
Send from BB using Exchange Acct (BES)
Fails with:

The message cannot be delivered due to a configuration error on the
server. Please contact your Administrator.

On desktop (Mac), Forward the failed message w/pic attachment to the original intended web gallery

Pic shows up in gallery as it should.

Now.. emailing pics to another email address works fine, it's just the web galleries that fail from the BB when using the exchange acct.