This often leads to duplication of emails. The inaccurate configuration of Microsoft Outlook gets regulated when two or more “ move a copy to” rule is applied to specific incoming emails. Such instances frequently happen if you activate the option of “ Leave Messages on the Server”. The technical issue in the mail server is also a reason behind the duplication of Outlook items. While creating an account in Outlook, if the mailbox parameters are set inappropriately, then it is likely to receive same email and any message for multiple times. This can be one of the reasons for email duplication in the Outlook mailbox. If the same email account is used in different devices, i.e., laptop and mobile, then it will cause repeated synchronization of the incoming message. If the inbox updates with low frequency, the emails and other data in the mailbox will not get synchronized and will lead to duplication of data.