We use Exchange 2007. When we send to certain domains (just one or two that I know about), we get an undeliverable back saying something like: #5.0.0 smtp;550 RCPT TO:<email@example.com> Relaying not allowed - please use SMTP AUTH>.
Is this because of a DNS/IP issue or something with the SMTP header?
I'm just using a Send Connector with Address Space as Type SMTP and Address *. Under Network I'm just using DNS records to route mail (no TLS). The Source Server is just my "Default-First-Site-Name" Exchange Server. I have specified our FQDN for the HELO/EHLO response.
What am I doing wrong and/or what can I do to make the destination server accept emails from my server?
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