ME020470 - TRB: Duplicate messages may occur as a result of URL blacklisting or file locking contention


SYMPTOMS

Local or remote recipients may receive duplicate copies of messages.

CAUSE

There are three possible causes of this issue, each of which are explained below:

URL Blacklisting DNS Lookup timeouts

A remote mail server sends a message to a MailEnable server and timeouts occur during the DATA command. This may occur if the option to perform URL Blacklisting tests when messages are received has been enabled. The process of checking URLs for spam links may cause the remote client to timeout. Such timeouts will cause the remote mail client to resend the message, hence producing duplicates.

Contention when accessing MailEnable Queues

An external application is causing file access contention to MailEnable queues or to the MailEnable antivirus scratch directory. 

Third Party Pickup Event or Mailbox Delivery Event

If third party MTA pickup events or mailbox delivery events are being used, message duplications may occur if the pickup event is failing or has not correctly handled its queue management.

RESOLUTION

URL Blacklisting DNS Lookup timeouts

Review and consider reducing the number of URL blacklist providers being used. In particular, ensure that the blacklist providers being used are still in service.

Contention when accessing MailEnable Queues

Ensure that any resident anti-virus application is configured to exclude the MailEnable queues and scratch directory from protection (assuming the antivirus application allows this).

Third Party Pickup Event or Mailbox Delivery Event

If third party MTA pickup events or mailbox delivery events are being used, then it would be advisable to temporarily disable these as a potential cause of message duplication.



Product:MailEnable (All Versions)
Category:Environment
Module:SMTP
Keywords:Duplicate Duplication Multiple Messages mutliples emails mail message
Class:TRB: Troubleshooting (Configuration or Environment)
Revised:Wednesday, May 4, 2016
Author:
Publisher:MailEnable