Have Domino server sending e-mail to Exchange server group/distribution list. Message is dying with:
#< #x.x.x smtp; 550 x.x.x RESOLVER.RST.AuthRequired; authentication required> #SMTP#
Domino admin is saying that Exchange side is blocking because of spam rule, Exchange side all is well and issue must be Lotus Domino side. Answer is that it is in the AD properties of the distribution list that is part of the SendTo list.
The Exchange / AD Distribution List (group) has been set to only allow certain people (or not anonymous) to send mail to that group. If this is on purpose, then nothing needs to be done except tell someone not to give out that e-mail address because it's restricted. If it was enabled accidentally, the restriction can be removed by doing the following:
1. Start the Exchange Management Console.
2. Locate and highlight the distribution list that is restricted.
3. Choose (or right click) Properties.
4. In the Properties dialog, choose the Mail Flow Settings tab.
5. Select, click the Message Delivery Restrictions item. Once again, click the Properties button.
6. In this Properties dialog, deselect the check-box Require that all senders are authenticated.
7. Click the OK button close that properties box.
8. Click the next OK button to close the original properties box.
9. Close the EMC if desired.