Regarding the “550 5.6.0 Lone CR or LF in body ” error:
I see that you posted this issue to the IBM Lotus forum a few days ago, but have yet to receive a reply. Although I do not have a specific answer for you regarding the delivery failures you are seeing, the fact that your information (as detailed in your previous IBM post) indicates that a “point” upgrade to your Domino server fixes the issue would seem to be the resolution you are looking for. To my experience, when a point update is issues for a Domino server release, there may well be un- or poorly documented fixes included with the update release code. I would attempt to update your server installation if possible and see if the issue resolves.
Have you looked on SearchDomino for a solution? Perhaps ther may be one posted or discussed there….
Regarding the “4.4.1 Did not receive the expected protocol response” error, I have been unable to find any answers to similar questions posted on several forums (including TechNet) going back to 2004. Sorry…