Duplicate emails may be received when Premium Antispam (PAS) feature is enabled. The duplicate ones may arrive in random periods. Same Message ID is observed in the email internet headers for both the original email and duplicate ones.
Currently in SMSDOM for Windows, email processing works in such a way that whenever spam definitions are being downloaded, SMSDOM PAS halts the email processing. It waits for the definition download process to complete and will then resume the email processing.
As email delivery is delayed due to the product behavior, this may cause sending server to resend the emails and create duplicate emails.
The issue may be observed on machines with SMSMDOM 32 bit installed.
Symantec is aware of this issue and is planning to resolve it permanently in future build. It may not be necessary to log a support case on this issue. Please subscribe to this article to be notified of any updates.
Domino server 8.0.10 (32 bit)
Windows 2003 SP2 (64 bit)
Symantec Mail Security for Domino (SMSDOM) 8.1.2 (32 bit)