Solved

Spam Relay Problems

Posted on 2009-05-05
7
364 Views
Last Modified: 2012-05-06
I hope someone can shed some light onto thiw. None of the solutions I have found have worked.

A customer has an SBS 2003 server running exchange. They use SMTP for both incoming and outgoing mail.

Someone is sending 1000's of mails through their server as postmaster@theirdomain.com

I have tried all sorts to block them but they appear to have random IP addresses. If I disable SMTP relay then nobody can send or recieve mails. If I turn on authentication then outside servers cannot send mail to their mail server.

Hope someone has come across this before.

Thanks in advance
0
Comment
Question by:jgearhart
  • 3
  • 2
  • 2
7 Comments
 
LVL 24

Accepted Solution

by:
Rajith Enchiparambil earned 300 total points
Comment Utility
This is NDR attack. Configure recipient filtering, smtp tarpitting.

Follow this article in full http://www.amset.info/exchange/spam-cleanup.asp

http://enchiparambil.com/smtp_tarpitting_for_exchange.aspx

Rajith.
0
 
LVL 24

Assisted Solution

by:Rajith Enchiparambil
Rajith Enchiparambil earned 300 total points
Comment Utility
0
 
LVL 11

Assisted Solution

by:g000se
g000se earned 200 total points
Comment Utility
Helllo,

In Exchange look under- Message Delivery.  You can block the Spam
0
IT, Stop Being Called Into Every Meeting

Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

 

Author Comment

by:jgearhart
Comment Utility
I have checked using telnet and according to that the system is secure. I am at a loss to explain how they are managing to send mails through the server. They are sending them using out own postmaster address which I understand cannot be disabled.

The mail is going out FROM the server as postmaster not incoming as postmaster.

Is there a way to secure this so that only the system can recreate an outgoing mail as postmaster?

I have managed to stop the mails from leaving the server but they are just backing up in the queues now at a rate of about 600 per hour.

Any suggestions?

I have a watchguard x10e by the way if anyone has any suggestions on additional configuration options.
0
 
LVL 24

Assisted Solution

by:Rajith Enchiparambil
Rajith Enchiparambil earned 300 total points
Comment Utility
have you configured IMF in Exchange 2003, especially sender id filtering? What about smtp tarpitting?

Configure IMF as a measure to fight spam. In your case, it seems like the spammer is sending emails to non-existent users in your domain and your server is responding with an ndr when the user is not found.

http://www.petri.co.il/block_spam_with_exchange2003_imf.htm
0
 
LVL 11

Assisted Solution

by:g000se
g000se earned 200 total points
Comment Utility
Using the message delivery in Exchange is a no cost solution in fighting against SPAM.  You can also block it at the client level too in Outlook.
0
 

Author Closing Comment

by:jgearhart
Comment Utility
I managed to solve the problem using the watchguard SMTP proxy built into the router.

This seems to be the solution with the lowest resource overhead since the server is not particually powerful.

I basically told the router to reject all mails in both directions for postmaster@domain.com

This seems to have cured the problem.

Many Thanks for all your comments

I have split the points between you because nobody came up with a solution that solved the problems but you all pointed me in the correct direction.

0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

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.
Scam emails are a huge burden for many businesses. Spotting one is not always easy. Follow our tips to identify if an email you receive is a scam.
In this video we show how to create a Resource Mailbox in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.: Navigate to the Recipients >> Resources tab.: "Recipients" is our default selection …
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…

762 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

11 Experts available now in Live!

Get 1:1 Help Now