Duplicate emails are one of the most annoying conditions that Outlook users face. It makes PST files unnecessarily big and consumes data storage. Both senders and recipients face the problem. It all happens because multiple copies of emails are stored in the recipient's inbox and sent item folder as well as Outbox.
The problem is annoying and is not acceptable. You can deal with the duplicate issue to some extent. Below are some common configuration issues leading to duplicate emails and how to deal with them.
Outlook Integrated with Virus Scanner
When a virus scanner is integrated with MS Outlook and is also installed in the machine, the problem of duplicate emails can increase. It is because the scanner scans outgoing emails also.
So, it is recommended to disable the Virus scanner if it is causing duplicate email issue. It will allow Outlook to perform smoothly.
Setting of Short Time Intervals of Sending and Receiving Data
When send/receive of emails gap is for a short period of time, less than 5 minutes, the problem email duplicate can be faced. It happens because when Outlook is processing the first email to upload in the mail server to send or receive, the next email process is started before finishing the previous. Thus, it causes the accumulation of the send/receive process. The messages stored in the Outlook have submitted again. It is how a duplicate email problem is initiated.
To resolve the problem by checking the backlogs and increasing the time gap of send/receive files.
To Evaluate Backlogs
For Outlook 2007 and Below Version-
Go to Tool, then send/receive and setting window of send/receive and then evaluate the progress.
For Outlook 2010 to 2013
Under the 'View' tab, press 'Show Progress' tab
Change the Time Gap
In Outlook 2007 and Below Versions
Press 'Tools' and 'Option' tab
In the Options Window, hit the button Mail Setup and then send/receive to change the time gap.
In Outlook 2010 and 2013
First go to File tab, from the drop-down 'Option', 'Advanced' tab and later send/receive for alerting time gap
Note: Set the time period for more than 5 minutes. If you are handling more than one account, the time duration should be 10 minutes.
Poor Connection to Mail Host
It can be the reason for duplicate emails. It is all because both IMAP and POP3 accounts function with server timeouts. When the server connection is poor, the server may time out. Thus, Outlook re-submits the Outbox message for the next schedule. It creates duplicate emails.
Increasing the server time-out can fix the problem of duplicate. It is all about increasing internet speed. Reset the internet time-out and increase the server timeout to 2-3 minutes.