IBM Lotus Notes/Domino 8.5 Forum (includes Lotus Notes Traveler)
Not much else I can say
There are many possible reasons and I'm sure that I don't know them all. If I had this situation with my own server and I couldn't determine the cause, I would try contacting the postmaster at one of the domains that is rejecting messages.
Feedback response number WEBB8JNP44 created by Rich Schwartz on 07/11/2011