We have an Exchange 2007 server (1 server setup)
One user have problems to send mail to few customers. (He is the one ho send most emails)
There are three different errormessages:
#553 sorry, that domain isn't allowed to be relayed thru this MTA (#5.7.1) ##
#550 5.7.1 <name@domain.net>... Authentication required
#550 5.7.1 Unable to relay for Anyone who have a solution?
pem