[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now


#5.5.0 smtp;550 Recipient unknown error when sending from a secondary domain.

Posted on 2006-05-09
Medium Priority
Last Modified: 2008-01-09
My exchange server is taking care of email for 4 domains, a.com, b.com, c.com and d.com. a.com is my primary domain that I set up when I first set up exchange. the other 3 domains, b c and d, are extra domains I've purchased and added in on the recipient policies to receive email on. This has worked great for me so far.

The problem comes now when one of my users needs to be able to send email from b.com rather than a.com. I went into his active directory user profile, and changed his primary email address from user@a.com to user@b.com. Every time they send email from that address to an outside address they receive the following error:

Subject: test
Sent: 5/9/2006 12:28 PM

The following recipient(s) could not be reached:

  outsideuser@outsidedomain.com on 5/9/2006 12:28 PM
  There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
  <a.com #5.5.0 smtp;550 <outsideuser@outsidedomain.com>, Recipient unknown>
I've also tested this with domains c.com and d.com, they have the same issue

I know that the MX records are set up correctly, I've checked them on dnsstuff.com. I also know that the address I am trying to send email to is correct.

I've tried using telnet to track down the problem (http://support.microsoft.com/default.aspx?scid=kb;EN-US;153119), but had no luck.

I saw a Microsoft article saying that it may be the outsidedomain.com's firewall, however I know this is not the case as email sent from a.com goes through with no problems

Lastly, the emails all work correctly internally, its just when I try to send over the internet that I receive the error.

Thanks in advance for the help!
Question by:bigft14CM
LVL 104

Accepted Solution

Sembee earned 1500 total points
ID: 16650380
Is the second domain setup the same as the first domain?
I usually recommend that they are configured identically - same MX records etc, so that you don't have any problems with the reverse DNS lookups. If the server is announcing itself as domain.com and not host.domain.com then other sites can have issues with that.

Therefore the first thing I would suggest is to check your DNS is configured correctly.

Do you send email through a smart host? If so, you may want to check the smart host will allow the other domains to be sent through it.


Author Comment

ID: 16651598
That didn't exactly help, but it pointed me in the right direction. I routed my smart host to relay mail through my ISP's mail server and now everything works.


Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

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

How to effectively resolve the number one email related issue received by helpdesks.
This article will help to fix the below errors for MS Exchange Server 2016 I. Certificate error "name on the security certificate is invalid or does not match the name of the site" II. Out of Office not working III. Make Internal URLs and Externa…
In this video we show how to create a mailbox database in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center. Navigate to the Servers >> Data…
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
Suggested Courses

867 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