Remove Duplicate Messages

Main features

• Removes duplicate emails in Outlook folders, Exchange and Office 365 mailboxes, as well as Exchange Server public folders.
• Enables moving duplicate messages to the specified Outlook folder, to bring them back to their original locations, if necessary.
• Deletes duplicate Outlook emails from one or multiple folders at once.
• Removes duplicate emails in Outlook PST data files.
• Allows setting your own criteria to specify what messages are duplicates.
• Removes duplicate Outlook emails in bulk and by schedule with command line app.

Why Outlook duplicates emails and how to prevent the email duplicating

The reasons that may cause email duplicating in Outlook may be different. Here is the list of the 7 situations that provoke repeated emails in Outlook and the ways to avoid the problem.

Outlook rules configuration

One of the most common causes of duplicate emails in an Outlook mailbox is the rule configuration. For each incoming message, Microsoft Outlook applies all the rules together. Those can be several "Move the item to folder" rules, plus others.

Solution: Check your Outlook rules to ensure that you haven't any rule combination that causes duplicates in your Inbox. Activate the stop processing more rules action for those rules that result in duplicate emails in Outlook when applying together.

Synching Outlook account on multiple devices.

When working in the same Outlook profile on different devices, such as desktop, tablet or mobile phone, messages are often synchronized multiple times. Synchronization failures and errors lead to duplicate emails in Outlook.

Solution: Check the Task Manager to ensure you have only one outlook.exe running while synching. Several processes running simultaneously is not unusual and may create duplicates in the mailbox. End the duplicative processes and resume your synchronization.

Using multiple Microsoft Outlook accounts

To separate your mail, for example, work and personal, you will use different profiles. However, some Outlook users do not actually use different accounts, but use aliases for the same email account. If you use aliases, the same mailbox can be configured twice, resulting in double emails in Outlook.

Solution: Use different accounts and not just aliases. If you still prefer to keep using aliases, uncheck "Receive mail items" in the alias account settings to avoid receiving and sending duplicate emails.

Sending/receiving intervals

When the time between sending and receiving data is short (a few minutes), this can also cause the problem of duplicate emails. Outlook doubles emails because it does not have time to complete the processing of one request to download / receive data through the mail server, as the next one is already starting.

Solution: The obvious decision is to set the send/receive interval longer. Widen the Inbox update frequency by defining Send/Receive Groups:

1. Open the Send/Receive Groups window.
2. Set the Schedule an automatic send/receive every value to something over 15 minutes.

Using an antivirus

If Microsoft Outlook and an antivirus program are installed on the same computer, Outlook may interact with the virus scanner as an intermediary between the mail client and the server in sending and receiving the mail. If the virus scanner is not configured properly, it does not close the connection to the mail server and the email message is not flagged as received. Some antiviruses may also fail when processing corrupted emails. As a result, you receive the same messages during the next Send/Receive cycle.

Solution: Check the instruction manual of your antivirus software on how to disable email protection when integrating it with Outlook.

Outlook is configured incorrectly

In case of restoring an Outlook profile (on the new computer or for another reason), the original account setting Leave a copy of the messages on the server (POP3 account) will create duplicates of all the previous messages downloading them as "new" ones.

Solution: Once you have reconfigured Outlook, start it with a new clear PST file before reconnecting the old PST and setting it as the default delivery location. This way, you'll get all the existing emails in a new PST file. After that, merge PST using the advanced version of the utility to avoid duplicates.

Adding PST file to current Outlook profile

For Outlook backups, most users export their mailbox to a PST file. Then, when importing this data file into the same Outlook profile it was exported from or when merging PST files, Outlook items are also duplicated.

Solution: Use a professional tool for the PST import into Outlook to avoid, find and decide what to do with the duplicates.

5 good reasons to remove duplicate emails in Outlook

1. Identical messages lead to mailing chaos. You don't know for sure whether the message was replied to or not. If you reply to the same email multiple times, it will lead to problems in communication.
2. Message copies are garbage that litters the mailbox. As a result, the entire mailing system starts to run slower, meaning your productivity drops. You spend more time composing and sending messages. If the mailbox is limited in size, you must think carefully about what to delete to clean up space.
3. Many duplicate emails in Outlook folders slow down the search. Sometimes, you may find that Outlook freezes. In fact, it's indexing the large files and mailboxes - duplicate items make a mess in search for the right email messages.
4. Duplication in Exchange and Office 365 public folders slows down the workflow. Some groups of people open and see replies to messages; others might miss them. Thus, it takes more time to complete many tasks, and the work efficiency decreases.
5. If duplicates crowd your mailboxes, you need more space to create backups. At some point, a backup copy of your mailbox won't fit on your disk drive or network share. Or cloud storage pricing plan.

How to remove duplicate emails in Outlook with the built-in tools

There are 4 basic methods to remove duplicate emails in Outlook.

1) Delete duplicate emails with Outlook Account Settings

An Outlook data file (PST) can be configured multiple times. Then, when synchronized in Outlook, the accounts, and therefore the messages, are duplicated. Here, you need to delete redundant accounts.

1. Go to File > Info > Account Settings > Account Settings.
2. On the Email tab in the "Account Settings" window, browse through the configured accounts. If the same account name appears more than once, delete duplicate accounts.
3. To do this, highlight the account by clicking on it and tapping the "Remove" button.
4. Close the window. The unnecessary accounts are deleted completely.

If you're still bothered by duplicate emails after this, use these solutions.

2) Remove duplicate Outlook emails with Import/Export tool

1. Go to File > Open & Export > Import/Export.
2. Select Import from another program or file.
3. Click Outlook Data File (.pst) and then Next.
4. Browse to the .pst file and mark Do not import duplicates.
5. Select the required folder to import, mark Include subfolders and Import items into the current folder. Then click Finish.

After applying this method, you still can have the duplicate messages in some folders. If so, use the next inbuilt feature of Microsoft Outlook.

3) Delete duplicate emails with the Inbox Clean Up option

1. Go to Home > Clean Up.
2. Now, choose the desired option:
   • Clean Up Conversation to move duplicate messages from the conversation to Deleted Items;
   • Clean Up Folder to delete duplicate emails from a particular folder;
   • Clean Up Folder and Subfolders to run the cleanup process across the folder and subfolders.
3. Then go to the Deleted Items folder to check the removed duplicate emails and delete them permanently.

Although the Clean Up tool is often helpful to deduplicate Outlook emails, it doesn't always work perfectly. Sometimes you can receive an error report "No messages were cleaned up. Only messages that satisfy your Clean Up Settings will be moved to the folder."

4) Remove duplicate Outlook emails manually

If this is the first time you have encountered the problem of duplicates, the easiest way may seem to be manual deletion.

If you have only several messages, you can Change View of the current Outlook folder to table mode and delete those items you think are duplicates. Or, in the View Settings, group messages by selected criteria using Columns... or Group By... and then eliminate duplicate emails that you find.

But if you receive duplicate emails occasionally and you already have a lot, there is a high probability that you may delete important data by mistake. And if duplicates are in different folders, it's very hard and time-consuming to delete them manually. Most likely, you'll miss something or delete more than needed.

All four out-of-the-box Outlook email management tools can work if you have a small PST file with a few dozen emails. But in the vast majority of cases, the situation is quite different - hundreds of messages in multiple folders. And when they duplicate, you need a professional tool with flexible settings and a simple interface. Such a tool will quickly remove duplicate emails in Outlook without losing time and nerves.

How to delete duplicate emails in Outlook with automatic remover tool

If there are tons of duplicates in different folders, this becomes a difficult problem to solve. Our Outlook duplicate email remover will save your time and keep you from errors.

Three ways to remove duplicate emails

1. Outlook add-in. Deletes duplicate emails directly in Outlook. You can remove duplicates from selected messages or folders using the context menu of a folder. Add the tool on the Outlook ribbon to use it frequently and delete duplicate emails in a couple of clicks.
2. Standalone app. Removes duplicates with no need to start Outlook. Allows you to connect and disconnect PST files without creating new Outlook profiles.
3. Command line. Removes duplicate Outlook emails in scripts, batch files, and by any schedule. Using the command line during email migrations between computers and servers is convenient.

Tips for removing duplicate messages

• Remove duplicates from any Outlook folders, including Search Folders. When deleting duplicates, you can use any Outlook filters, just create a suitable search folder and delete duplicate emails in it.
• In a standalone app, you can indicate PST files when selecting folders. You can delete duplicate emails from the PST file list using the power of the command line.
• The utility removes duplicate Outlook emails from Exchange Server and Office 365 mailboxes. Supports both cached and online modes. To remove duplicate messages from other users' mailboxes, use the command line or connect additional mailboxes in Outlook.
• Deduplicate email messages from Exchange and Office 365 Public Folders. Using the folder priorities, you can leave messages in some folders and remove duplicates from others.
• Move duplicate messages to the selected folder, instead of removing them permanently.
• You can delete duplicate emails among selected Outlook messages or folders when using the add-in.

How to determine that messages are duplicates?

The answer to this question is not as obvious as it may seem at first glance. When you have hundreds of duplicate emails in an Outlook mailbox, it may be difficult to determine them. Our add-in offers easy ways to recognize duplicates automatically.

To understand which emails are duplicates, you must compare their fields and properties. Check Use custom fields to compare on the General tab when configuring the advanced version of the utility.

Comparison by fields

On the Advanced tab, you can select the fields for comparison: subject, text, sender, recipients, and attachments. If those fields have the same values, it can be concluded that messages are duplicated. Dates are rarely used to detect duplicates because duplicates are often several identical messages sent at different times.

Detecting duplicate emails within a date range

If you know exactly when duplicates appeared, for example, set the filter by dates over the last few days.

Deleting duplicate emails over the past week will work much faster than removing duplicates from the entire mailbox or data file. When periodically removing duplicate Outlook emails from public folders, it is enough to complete deduplication once. In the future, it is better to use a constrained deletion, for example, only for the last month.

What can you do with duplicate emails in Outlook?

• Move duplicates to the specified folder. By default, this is the "Deleted Items" folder. The utility will move duplicate messages to the selected folder, preserving the original structure. Here, you can recover removed Outlook duplicate emails using the Merge Folders utility.
• Remove duplicates permanently. This way, the duplicate emails are not being moved anywhere but simply deleted. This option is also useful if your Outlook store doesn't contain the "Deleted Items" folder. For example, if you remove duplicates from public folders. Before using this mode of duplicate removal, it is useful to first check the report from the Duplicate Outlook Items Report.
• Assign the specified Outlook categories to duplicates, mark them with a flag or set their expiration date. To do this, run the Find Duplicate Messages utility.

Removing duplicate Outlook emails from one or more folders

If duplicate messages are in different folders, set the Search duplicates across the folders option. Here, the remover first searches for duplicate emails in all selected folders, and only then deletes them.

To keep original messages in their places, specify the folder priorities. For example, when using Outlook/Exchange rules to sort received messages in different folders, adding the "Inbox" to the low priority list is convenient. Here, messages sorted by rules will always be considered originals, and duplicate emails in the Inbox will be deleted.

When searching for duplicates in multiple folders at once, your messages will remain in some places, and duplicate emails in other places will be deleted. Configure folder priorities to specify which to leave messages in.

Add any Outlook folder to the high or low priority list. The utility leaves the same messages in the folders with the highest priority. Duplicates in the folder with a lower priority will be deleted. If you don't use the folder priorities, the utility will delete the recent messages, leaving older ones.

Removing duplicate emails in Outlook during email migrations

Migrating mailboxes from other mail systems or mail programs is a complex process fraught with errors and failures. Sometimes, user mailboxes or public folders are migrated to a new system along with redundant duplicates. To address such problems, often unique to the particular organization, the ability to remove duplicate Outlook emails using a command line is provided. You can specify the list of mailboxes, public folders, and PST files requiring mass deduplication as a command line parameter. You can use the command line application in your Windows PowerShell scripts, batch files and other scenarios.