Monday, 24 October 2011

Reverse DNS

So after setting everything up on my side I figured mail was sorted....... Wrong. Users started to complain that they where getting bouncebacks giving an error about authentification:

"coombes.uk-noc.com gave this error:
Not authenticated, please enable SMTP Authentication in email software and check login credentials
A problem occurred during the delivery of this message to this e-mail address. Try sending this message again. If the problem continues, please contact your helpdesk."

After a long time looking around a great exchange Guru on technet pointed me to this site http://www.mxtoolbox.com/supertool.aspx

You put the email domain in and choose lookup. Then select mx lookup and then click smtp next to the MX record. For me this showed that reverse DNS had failed. It also came up with a few other errors which I resolved.

After much research I found that reverse DNS has to be set by the ISP. I contacted the ISP who hosted my domain and asked them to create reverse dns to match the A record that was set for mail. eventually I received a response that they did not own the IP I wanted the record for. Turns out although they hosted the A record ad such and hosted the domain they did not provide our internet IP address range. I contacted the ISP who host those IP's did asking the same.

They changed it and it worked.

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