?
Solved

Exchange error sending to certain domains "421 4.2.1 unable to connect"

Posted on 2014-10-28
2
Medium Priority
?
1,244 Views
Last Modified: 2015-01-23
I am not an exchange guru but I know enough to be dangerous.
I havs an SBS2011 with Exchange 2010 for my business (5 users). Mail is working for the most part however there are a few domains that we can not send mail to. The messages sit in the queue until they finaly fail. The error we are getting is:

451 4.4.0 Primary Target IP address responded with: "421 4.2.1 unable to connect." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.

95% of our messages get delivered just fine, with the exception of a few domains where we get the above error. We are not on any SPAM blacklists. I don't know where to begin.

Please help.
0
Comment
Question by:wilkox1
2 Comments
 
LVL 16

Expert Comment

by:Postmaster
ID: 40409988
Try an MX record lookup (http://mxtoolbox.com/SuperTool.aspx#) of the destination SMTP domain.
This will show you the public IP for that mail server - make sure your system is talking to the same IP that is shown.

It may be that you have an entry in your own DNS for that domain - if so remove it to force the lookup to go external and get the right IP.

If the IP looks OK - then you may need to contact the IT support of the company and seek an advice.
0
 
LVL 12

Accepted Solution

by:
Md. Mojahid earned 1500 total points
ID: 40409993
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Exchange database can often fail to mount thereby halting the work of all users connected to it. Finding out why database isn’t mounting is crucial and getting the server back online. Stellar Phoenix Mailbox Exchange Recovery is a champion product t…
Upgrading from older Exchange server to the latest Exchange server can be tiresome, error-prone and risky, without being a seasoned exchange server administrators. It can become even problematic if you're an organization that runs on tight timeline…
The video tutorial explains the basics of the Exchange server Database Availability groups. The components of this video include: 1. Automatic Failover 2. Failover Clustering 3. Active Manager
To add imagery to an HTML email signature, you have two options available to you. You can either add a logo/image by embedding it directly into the signature or hosting it externally and linking to it. The vast majority of email clients display l…
Suggested Courses
Course of the Month12 days, 23 hours left to enroll

579 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