Hi,

We have exchange server 2013. The issue is that emails are stucked in queue for one domain. We have no issue sending emails to all other domains i.e gmail, yahoo etc'

Users are getting the following messages:

Remote
Server at mail.server.com (xxx.xxx.xxx.xxx) returned '400 4.4.7 Message
delayed'

3/22/2015 2:26:30 AM - Remote Server at mail.server.com
(xxx.xxx.xxx.xxx) returned '451 4.4.0 Primary target IP address responded with:
"421 4.4.5 Service not available, connection deferred." Attempted
failover to alternate host, but that did not succeed. Either there are no
alternate hosts, or delivery failed to all alternate hosts. The last endpoint
attempted was xxx.xxx.xxx.xxx:25'

Any thoughts please?

Regards,

Anees

Hello

tip:check remote smtp server with telnet

we are able to connect smtp via telnet. is there anything we should do at sending or receiving site. We are admin of both servers.

Hello

telnet remote server 25 and
helo
mail from: email@address
rcpt to: email@address
data
test
.

on the remote site haven't got cisco firewall? https://support.microsoft.com/en-us/kb/320027

Hi Anees,

Thank you for your question.

We could make sure this specific domain is online and available, then we use gmail account send email to this domain to check if it successed, if gmail could send email to this domain without any problems, we could run the following command to check if the issue persist:

Set-SendConnector -Identity "<SendConnectorName>" -IgnoreSTARTTLS $true

If the issue persist, we could check firewall and network device to check  if they blocked it.

If there are any questions regarding this issue, please be free to let me know. 

Best Regard,

Jim

Hello Anees,

Would request you to please the firewall first and also network device to check  if they blocked it.

For More Info on NDR Codes:

http://www.techrid.com/exchange-server-2010/mailflow/exchange-server-mail-flow-troubleshooting-with-list-of-exchange-2010-ndr-codes-2/

Regards,

Praveen

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