I had the same problem for a particular domain(ex.abc.com). I couldn’t get any solution for this issue from internet too. Finally, i did a trace from the server console to that domain (abc.com). The DNS lookup used by the server to send out mail returned a wrong IP address for the domain(i knew it’s wrong because it’s one of our client’s domain).
Please check the IP address of the domain and try to correct it in the DNS server Or add a local entry in the server machine’s host file.
(like xxx.xxx.xxx.xxx(mx entry IP address of the domain)abc.com)
Now try to route the mails to that domain. It should work.
Subject: “SMTP Protocol Returned a Permanent Error 550 No such domain at this location”
These delivery failure messages are received when trying to relay mail through your Domino server with a firewall between the sending and receiving server?
If so, the reporting MTA of the delivery failure could be your firewall then verify that you are not configured to not allowing relaying. Changes needed to be made on the firewall to allow relaying.