Hi experts, hoping for some assistance with this;
We have implemented a new SBS2011 server which appears to be unable to deliver mail to any remote server that uses sender address verification.
When I test using telnet from our server to one of the remote servers giving us trouble I get the following:
220 remote.safenetbox.biz ESMTP NetBox(tm)
250 2.1.0 Ok
450 4.1.7 <email@example.com>: Sender address rejected: unverifi
ed address: lost connection with mx.mydomain.com.au[188.8.131.52] wh
ile sending RCPT TO
The mailfrom address is a legitimate address which I can send email to. There were some dns issues previously with the ptr and mx records however I can now verify the primary mx, ptr and smtp banner all match. At first glance it would appear to me that when the remote server does an rcpt to test on the sender address it fails, but why?
The setup is very simple; a virtualised SBS2011 machine sitting behind NAT; the primary mx is the WAN IP and we are not using a smart host to deliver mail. Appreciate any assistance.