Spam Blocking

The University receives an average of 26 million spam messages each month.  To help block a higher quantity of spam and to reduce the load on ND servers, as of February 28 we subscribed to the Spamhaus database. This is a database of systems recognized as excessive sources of spam or which have been identified as compromised and in the control of spammers and hackers.  This enables us to block a larger percentage of spam from reaching your mailbox and spam quarantine.  Plus, the database will help correct the recent performance of email delivery. 

Spamhaus is a leading provider of real-time anti-spam protection for Internet networks, and it works with Law Enforcement to identify and pursue spammers worldwide.

How Spamhaus works with our servers

Spamhaus maintains a database that includes:

• IP address of systems that have been identified as egregious sources of spam, or which have been identified as hijacked systems controlled by spammers and/or hackers; and
• IP space whose owners have identified the addresses as being used solely for dynamic address location, which means there should be no legitimate mail servers at any of those addresses.

ND mail servers are configured to check the Spamhaus database for every inbound message and reject messages from systems listed there.  If you find that ND servers reject legitimate messages from a specific source, it may be listed in the Spamhouse database or the senders email server may not be configured correctly.

What to do if legitimate email is being blocked

ND mail servers will reject email for several reasons, and the sender will receive a rejection message.

• ND mail servers will not accept messages from any system listed in the Spamhaus databases. When a message is rejected due to this policy, the sender will receive a  message which should contain the following error message:

Message rejected due to Spamhaus listing

• The sender should report this problem to their email administrator, so the email administrator can take appropriate action to get their mail server removed from the list. Additional information can be found at http://www.spamhaus.org/lookup.lasso
  

• Mail will not be accepted from any system which has missing, incomplete or conflicting DNS (Domain Name Service) information. The IP address of the system which connects to deliver a message must resolve to a hostname, and that hostname must resolve to the same IP address.  When a message is rejected due to this policy, the sender will receive a message which contains one of the following error messages:

Possibly forged hostname for x.x.x.x

or

 Fix reverse DNS for x.x.x.x

where 'x.x.x.x' represents the IP address of the sender's mail server.   

• The first message means that the IP address resolves to a hostname, but the hostname does not resolve, or does not resolve to the same IP address.
• The second message means that the IP address does not resolve.

In either case, the sender should report this problem to their email administrator so the email administrator can correct the DNS entries for their mail server, to ensure that their mail server has a matching set of A and PTR records in DNS.

Email Administrators: Click Here for Instructions on Diagnosing and Resolving this Issue  

If you need assistance in identifying the cause of the problem, have the sender provide you with a copy of the delivery error message they receive, either by FAXing a printed copy to you or by sending it to a personal email address you might use (e.g. gmail or hotmail).  Contact the OIT Help Desk (574-631-8111) with this information.

If you have additional questions spam filtering and blocking, please contact the OIT Help Desk (574-631-8111).