Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

Exchange 2003: 451 Could not complete sender verify callout

Posted on 2007-04-02
10
1,975 Views
Last Modified: 2008-01-09
I am trying to track down meaningful info on the following error and MS Exchange 2003 server.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
The following recipient(s) could not be reached:

      Cathleen (sales@domainredacted.com) on 3/17/2007 2:13 PM
            The e-mail system was unable to deliver the message, but did not report a specific reason.  Check the address and try again.  If it still fails, contact your system administrator.
            <smtp.mydomain.com #4.0.0 smtp;451 Could not complete sender verify callout>
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

It's only happening when the user sends to one particular domain.  What I've found so far leads me to believe that the recipient's server is trying to probe my server to verify the originating email account, and my server is not responding.  Some other sites suggested that it might be my server's problem.  

Can anyone help?
0
Comment
Question by:maamis
  • 4
  • 4
10 Comments
 
LVL 104

Expert Comment

by:Sembee
ID: 18838305
The recipient is doing some kind of lookup.

Put your domain in to dnsreport.com and ensure that everything is correct in there.
If you have any firewalls etc, ensure that they are not scanning SMTP traffic.

Do you have recipient filtering enabled? If not, turn it and the tar pit on. However don't set the tar pit for longer than 5 seconds.

Simon.
0
 

Author Comment

by:maamis
ID: 18838349
Did the DNSReport thing.  Everything is good in there.

I don't think I have recipient filtering on, and I don't know what the "tar pit" is...  Can you `splain that a liitle?  Thanks!
0
 
LVL 104

Expert Comment

by:Sembee
ID: 18838373
http://www.amset.info/exchange/filter-unknown.asp

It basically drops connections for users who are unknown.

Simon.
0
Does Powershell have you tied up in knots?

Managing Active Directory does not always have to be complicated.  If you are spending more time trying instead of doing, then it's time to look at something else. For nearly 20 years, AD admins around the world have used one tool for day-to-day AD management: Hyena. Discover why

 

Author Comment

by:maamis
ID: 18838476
Ok.  In the Message Delivery properties, "Filter recipients who are not in the directory" is checked.  I then went to the SMTP virtual server properties and checked the "Apply Recipient Filter" box.

Next, I did the tarpit.reg as outlined in your link.

But I'm not sure how this is going to help with mail we are sending out...
0
 
LVL 104

Accepted Solution

by:
Sembee earned 250 total points
ID: 18838695
The server is calling back to your server. It should now get something positive back immediately.

This isn't strictly an Exchange issue, it is standard SMTP things. It is a matter of trying to work out what the remote site is looking for.

Do you have anything else scanning SMTP traffic? AV, Anti spam, firewall, appliance etc? Those can trigger that message as well.

Simon.
0
 

Author Comment

by:maamis
ID: 18838763
We have GFI Mail Essentials for spam, but if I understand correctly, it's not looking at the port 25 traffic, it's looking at emails in the store.

Thanks for the help on this.  The user is trying her message again.
0
 

Author Comment

by:maamis
ID: 18851634
The problem still occurs.
0
 
LVL 104

Expert Comment

by:Sembee
ID: 18852850
You will have to contact the other side and ask them what they are looking for.

Simon.
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

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

Read this checklist to learn more about the 15 things you should never include in an email signature.
This article explains how to install and use the NTBackup utility that comes with Windows Server.
The basic steps you have just learned will be implemented in this video. The basic steps are shown to configure an Exchange DAG in a live working Exchange Server Environment and manage the same (Exchange Server 2010 Software is used in a Windows Ser…
This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online. The email signature template has been downloaded from: www.mail-signatures…

840 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