Email stops flowing or is very slow when Symantec Mail Security for Microsoft Exchange 5.0 and later running on Exchange 2003 is enabled.

Products

• Mail Security for Microsoft Exchange

Issue/Introduction

When you enable Symantec Mail Security for Microsoft Exchange 5.0 and later running on Exchange 2003, email stops flowing or becomes very slow. You use a Realtime Blackhole List to screen email senders.

Resolution

Symantec Mail Security for Microsoft Exchange supports the use of Realtime Blackhole Lists (RBL). An RBL is a list of mail servers that are known to pass spam. Symantec does not provide any RBL service. To use an RBL, you must subscribe to a third-party RBL provider.

Common problems with RBLs

• Incorrectly formatted domains
  You may use only valid RBL domains. If you use the incorrect domain for your RBL provider or if it is misspelled, your mail may slow or stop.
• RBL provider network problems
  If Symantec Mail Security cannot communicate efficiently with the RBL provider, email flow can slow or stop.
• Too many RBLs in use
  The use of multiple RBLs increases the time that Symantec Mail Security must take to check against the RBLs. Limit the number of RBL domains that you use.

If you suspect a problem with an RBL, contact the RBL provider for support. Symantec Technical Support suggests that you temporarily remove the suspect RBL from the RBL list to verify the problem.