Hello Montel! Perhaps, it is because you have two forwarding rules for the same primary mailbox and it forwards messages to Plumsail in both cases. Why do you need both of them? Could you test it with one of the rules disabled?
Thank you for working on this ticket. Our finance have two inboxes for two purposes; One for all queries and one for invoices. However I am still unsure as to how there is a duplication...theoretically, the emails from Primary inbox should just be forwarded to Plumsail and not remain in the Outlook Inbox.
To mitigate this issue:
I created a new shared mailbox, which is where all the tickets go to initially....before being forwarded to Plumsail, but just needed the explanation as to why the tickets remained in Outlook and Plumsail.
If you connect an Outlook mailbox to HelpDesk, you just provide access to the mailbox for HelpDesk. It does not prevent receiving and storing messages in the mailbox. In another case, when you forward messages, they can be kept in the mailbox optionally. In other words, HelpDesk does not interfere in functioning of an e-mail service.