We have phone systems at various customer sites that can send email messages for various purposes. The phone systems can only use port 25 SMTP to an IP address. Can not send to a FQDN which makes it a problem for a lot of ISP's who do not want to give out the IP address of their mail server. The phone systems will allow entry of a username and password for the mail account.
We are interested in using our own SBS2011 as a limited email relay for these systems. I have set up a receive connector to test with but cannot get it to relay. I am able to use a Telnet session to authenticate but when I get to the RCPT TO command the server returns 550 5.7.1 "your email message has been blocked by the recipient...."
Would appreciate any suggestions how to do this using SBS or another viable alternative.
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