This is for information in case somebody else gets the problem. After updating my Outlook 2007 with SP3 I tried to send out an email to a list I had containing 22 or 23 addresses in it. All came back with a 550 message saying the messages did not conform to 'x' (forgot what) protocol. I found that I could send up to 7 messages at once which just happened to be the number of Accounts I have set up in Outlook. When I tried to send 8 at once it would reject and the strange thing was when the messages rejected I got an additional message back with no body to it except that it referred to the last Account in my list of ISP account.

But the good news is that today I ran the 'Repair' option for MS Office 2007. It reported repairing one problem (not what it was, though). I rebooted the processor (Win 7 32 bit) and lo and behold, my original mail list went out perfectly.

Brad