Solved

451 4.4.0 primary target ip address responded with 421 4.2.1 unable to connect

Posted on 2016-10-12
10
52 Views
Last Modified: 2016-10-16
MS exchange q Viewer gives this below message
0
Comment
Question by:saul2paul
  • 3
  • 2
  • 2
  • +2
10 Comments
 
LVL 24

Expert Comment

by:-MAS
Comment Utility
Please mention the version of Exchange.
Please make sure your DNS working properly.
Please configure external for external lookup.
0
 
LVL 3

Accepted Solution

by:
Belal Khallad earned 500 total points
Comment Utility
The possible causes for the “451 4.4.0 Primary target ip address responded with: "421 4.2.1 Unable to connect." are:

 

1. Your hub transport server or edge server are unable to resolve the external domain names. It can be caused by the incorrect DNS sever settings.

2. Your firewall or ISP block the outbound traffics on port 25.

3. The IP address of your hub transport server or edge server are blocked by the target domain or other issues on the target domain.

The FQDN on the Receive Connector doesn't matter, that is inbound email only. It is only the FQDN on the send connector that is an issue. Ideally the FQDN on the send connector should match the PTR your ISP has set on your external IP address
0
 
LVL 3

Author Comment

by:saul2paul
Comment Utility
@mas, exchange on Prem 2010 , we have O365 federation service
0
 
LVL 29

Expert Comment

by:ScottCha
Comment Utility
What SP / RU level are you at?  You can find this by running the following Exchange PS command.

Get-Command exsetup | foreach {$_.FileVersionInfo}

Assuming this was a working environment, what, if anything, has changed?  New ISP, new SmartHost, network equipment...etc..
0
How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

 
LVL 14

Expert Comment

by:Todd Nelson
Comment Utility
This may or may not be related but review the article and check the NIC settings on the Exchange server...

https://oddytee.wordpress.com/2016/08/16/exchange-server-message-queue-error-451-4-4-0-dns-query-failed/
0
 
LVL 3

Author Comment

by:saul2paul
Comment Utility
the problem was with the SMTP port 25 on the firewall. Now its sorted
0
 
LVL 14

Expert Comment

by:Todd Nelson
Comment Utility
Belal should be award the points.
0
 
LVL 24

Expert Comment

by:-MAS
Comment Utility
Agree with Todd,
Belal cleary explained about the port 25 block to check in post
0
 
LVL 3

Author Comment

by:saul2paul
Comment Utility
sorry guys :) thanks for your feedback
0

Featured Post

Shouldn't all users have the same email signature?

You wouldn't let your users design their own business cards, would you? So, why do you let them design their own email signatures? Think of the damage they could be doing to your brand reputation! Choose the easy way to manage set up and add email signatures for all users.

Join & Write a Comment

Following basic email etiquette rules will help you write a professional email and achieve a good, lasting impression with your contacts.
Possible fixes for Windows 7 and Windows Server 2008 updating problem. Solutions mentioned are from Microsoft themselves. I started a case with them from our Microsoft Silver Partner option to open a case and get direct support from Microsoft. If s…
This tutorial will walk an individual through the process of transferring the five major, necessary Active Directory Roles, commonly referred to as the FSMO roles to another domain controller. Log onto the new domain controller with a user account t…
This tutorial will walk an individual through setting the global and backup job media overwrite and protection periods in Backup Exec 2012. Log onto the Backup Exec Central Administration Server. Examine the services. If all or most of them are stop…

772 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

14 Experts available now in Live!

Get 1:1 Help Now