returning emails (Submission from dynamic IP requires authentication)
Posted on 2014-02-23
We have an small domain network with Exchange 2010 server.
Our ISP told us we must leave automatic obtain IP on routers WAN interface, there is a reservation and we always get our IP address (we pay static IP).
When our exployees send emails, they sometimes get it back with error:
mx2.freenet.de #550 Submission from dynamic IP 220.127.116.11 requires authentication ##
18.104.22.168 is our IP
mx2.freenet.de is recipients mailserver.