HELO/EHLO error when sending to comcast addresses

I get an error anytime I (or anyone within my Exchange organization) sends an email to someone with a comcast address including replies.  We can send to all other addresses.  And can send to those addresses using other smtp or email accounts.  This is the error I get:

  *******@comcast.net on 7/17/2006 4:04 PM
            There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            <geek3.Coakley.local #5.5.0 smtp;521-EHLO/HELO from sender does not map to geek3.coakley.local in DNS>

How do I correct this?  I have checked the various blacklist sites, and I cannot find that we have been put on any of them.  I note that the difference in the DNS addresses above is geek3.Coakley.local versus geek3.coakley.local is the letter C in Coakley.  Is it case sensitive?  And if so how can I make this correction?  

Please give descriptive instructions as I am only a novice.  

Thank you for your help.
Who is Participating?
SembeeConnect With a Mentor Commented:
Your SMTP banner is incorrect and will fail some tests.

Anything ending in .local will fail.

You need to correct your SMTP banner, your reverse DNS and forward DNS.
See my web site here: http://www.amset.info/exchange/dnsconfig.asp

aiasslugAuthor Commented:
Do I need to make any changes on the DNS server in my network?  Like the forward lookup zones or reverse lookup zones?  Or do I just need to contact Verizon to verify that our PTR and MX records match?
Reverse lookup is set by your ISP, so you will need to contact them.
If your email is being delivered by SMTP then the forward DNS will be fine.

Changes to your internal network DNS are pointless - they will affect the internet.

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