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  • Priority: Medium
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Cannot sent emails to certain domains

Microsoft Exchange server cannot send emails to certain domains eg.AOL I get this error "5.5.0 smtp;550 DNS FAILURE" I asked my ISP to creating a PTR record in their DNS server which cannot be done because of an _ in the domain name. What can I do to fix this problem so that I can send emails to any domain?

Error Messege
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
  <mailserver.base_domain.com #5.5.0 smtp;550 REQUESTED ACTION NOT TAKEN: DNS FAILURE>
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1 Solution
you have an _ in YOUR domain name? That will complicate things a bit. A good deal of the time when mail delivery failures occur to specific domains, especially ones like aol.com, those domains do need a reverse DNS lookup on your outside IP to match the advertised name of your mail server.  If your ISP can't accommodate your domain, you may need to change your existing or purchase an additional domain name and use that for your mail server identification.

It also might be a good idea in your situation to make sure that your mail server is resolving DNS records properly. Depending on your mail server you can use nslookup or other such tools to lookup the MX record in the receiving domain.  Then you can try to telnet to that mail server on port 25 and see what you get.
Your other solution might be to find an ISP who can handle your request.
IrvingGAuthor Commented:
This problem has now been resolved by changing ISP. Thanks for al the help.
Great! Don't forget to accept a solution and close the question.

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