OTRS creates duplicate tickets while fetching

[crons]

We have confiugred 2 postmaster accounts

otrs_system1@domain.com - Queue1
otrs_system2@domain.com - Queue2

Customer 1 sends email to both email address, and cc to customer 2, it creates tow different tickets in Queue1 and Queue 2.
Customer 2 replies to all. OTRS creates a 2 tickets again instead of adding a followup to created a ticket. Also i see a error as:

Code: Select all

The MessageID '<B04A515BCAE7C34D90FEE204B055E3B25D35E79B9D@PHXCCRPRD02.domain.com>' is in your database more the one time! That should not be, a message_id should be unique! 

Postmaster setting in sysconfig
Ticket->Core::Ticket->Ticket::SubjectFormat - Left
Ticket->Core::Postmaster->PostmasterFollowUpSearchInReference -> Yes
Ticket->Core::Postmaster->PostmasterFollowUpSearchInRaw-> Yes.

Any idea on this?
Using OTRS 3.1.12 with MySql

[crythias]

alias/forward to one account.fetch once.