Solved

How does Exchange 2003 in SBS2003 R2 treat incoming email to invalid addresses at my domain?

Posted on 2006-10-31
2
295 Views
Last Modified: 2010-03-06
The reason for my question is I have just set up MailHop Backup MX at www.dyndns.com to be a backup server to my own SBS2003 Exchange server.
In their FAQ's they make the following point;

--------------------
Soft rejecting or accepting invalid addresses
When a message comes in for an invalid address at your domain, there are three things you server might do. It might

accept the message (and either deliver it to a default mailbox or send it to /dev/null)
reject the message with a soft/temporary error (4xx error code)
reject the message with a hard/permanent error code (5xx error code)
Either of the first two behaviors can cause significant problems. If you accept all such messages your server can become overloaded with junk mail sent as part of a directory harvesting attack. While this won't have an overly significant impact on your Backup MX, it prevents us from limiting the amount of junk mail sent through our system based on address verification.

The second behavior however can have much more drastic consequences. If you server is configured to issue a soft/temporary rejecting on messages addresses to invalid addresses, this will result in our system accepting messages for your domain and queueing them for delivery. We'll then end up queueing these invalid messages for up-to 10 days before we eventually bounce them. This can affect our ability to deliver valid email to your domain as we well as decrease the performance of the service for all customers.

For these reasons, we ask that you configure your server to follow the third path, reject all mail at receipt time with a 5xx level error message. This will allow our servers to reject those messages immediately and will help ensure the best overall performance for your domain.
--------------------

My question is; I'm fairly sure I'm not the first, but am I set up as the second or the third?

Thanks!
0
Comment
Question by:MPSmith4258
2 Comments
 
LVL 104

Accepted Solution

by:
Sembee earned 250 total points
Comment Utility
If you have recipient filtering turned on then Exchange sends back this:

550 5.1.1 User unknown

If you don't have recipient filtering turned on, then the messages are accepted and bounced immediately. This is bad practise and will get you blacklisted.

Simon.
0
 

Author Comment

by:MPSmith4258
Comment Utility
Thanks Simon, all understood
0

Featured Post

Why spend so long doing email signature updates?

Do you spend loads of your time carrying out email signature updates? Not very interesting are they? Don’t let signature updates get you down. Let Exclaimer Cloud - Signatures for Office 365 make managing email signatures a breeze.

Join & Write a Comment

Not sure what the best email signature size is? Are you worried about email signature image size? Follow this best practice guide.
Following basic email etiquette rules will help you write a professional email and achieve a good, lasting impression with your contacts.
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
how to add IIS SMTP to handle application/Scanner relays into office 365.

744 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

19 Experts available now in Live!

Get 1:1 Help Now