Exchange 2010 - Unable to send mail to one domain


I am having an issue sending an email to one particular domain, I get the error message delayed, and they sit in the exchange queue waiting to send.

The full error is as follows;

The message has been queued on server 'server.mydomain.local' since 9/24/2015 8:38:09 AM (UTC) Dublin, Edinburgh, Lisbon, London. The last attempt to send the message was at 9/24/2015 9:31:42 AM (UTC) Dublin, Edinburgh, Lisbon, London and generated the error '451-4.4.0 Primary target IP address responded with: " (mxeue103) Nemesis ESMTP Service not available 451-4.4.0 554-No SMTP service 451-4.4.0 554-Bad DNS PTR resource record. 451 4.4.0 554 For explanation visit" Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts

Emails on our side other then this domain is all working okay same on their side. And this has only just started to happen within the last couple of days. I can send mail to them from my gmail account.

When I telnet to the recipients server, I get the same message. I am pretty sure the issue is not with us, but it is with them can someone confirm this?

Vikash MohanTechnical DirectorAsked:
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Vikash MohanTechnical DirectorAuthor Commented:
Forgot to mention, i have checked our IP address, we are not listed on any black lists

Amit KumarCommented:
Please check telnet MX record on 25 port and see if that connects from your gateway SMTP/EDge server or Hub Transport server.

this issue is not your end issue is at recipient end.

Or it is possible they marked you in blacklisted on their gateway.

First try to telnet from your SMTP server on 25

telnet mxrecordrecipient 25

One more thing.. can you check PTR records for your domain's MX are they published properly just to verify.
Jeff GloverSr. Systems AdministratorCommented:
THe error says the PTR record is bad. You need up update the reverse DNS of your company to resolve the IP you send mail through.

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Vikash MohanTechnical DirectorAuthor Commented:

Thanks for your responses, When i telnet get the same error, never the less i have requested my ISP to change our reverse dns record so it is correct, I am awaiting their response, thanks.
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