Finding the same email in your Sent Items folder multiple times suggests Outlook is struggling with a corrupted send/receive setting. This is a common frustration that can clutter your inbox and confuse recipients, but the fix is often simpler than you think. If you have ever wondered “why is my outlook sending duplicate emails”, you are not alone—many users face this issue due to misconfigured accounts, add-ins, or sync errors. In this guide, we will walk through the most effective solutions step by step.
Why Is My Outlook Sending Duplicate Emails
When Outlook sends duplicates, it usually points to a conflict between your email client and the server. The problem often stems from multiple accounts configured incorrectly, a corrupted OST file, or an aggressive send/receive schedule. Let us break down the root causes and how to fix them.
Common Causes Of Duplicate Emails In Outlook
Before diving into fixes, it helps to understand what triggers this behavior. Here are the most frequent culprits:
- Multiple email accounts configured – If you have the same account added twice, Outlook may send each message twice.
- Corrupted send/receive settings – A damaged profile or OST file can cause Outlook to resend messages.
- Add-ins interfering – Third-party plugins like antivirus or CRM tools can disrupt email flow.
- Server-side rules – Rules that forward or copy messages can create duplicates.
- Outdated Outlook version – Bugs in older versions may cause duplicate sending.
Now, let us address each issue with clear, actionable steps.
Check For Multiple Email Accounts
The simplest reason for duplicates is having the same email account added twice in Outlook. This often happens after a reinstall or when migrating from another email client.
How To Verify And Remove Duplicate Accounts
- Open Outlook and go to File > Account Settings > Account Settings.
- Look for any duplicate entries of your email address. If you see the same address listed twice, select one and click Remove.
- Restart Outlook and send a test email to confirm the fix.
If you only have one account, move to the next step.
Repair Corrupted Send/Receive Settings
A corrupted send/receive group is a common cause of duplicate emails. Outlook uses these groups to sync with the server, and when they break, messages may send repeatedly.
Steps To Reset Send/Receive Groups
- Go to Send/Receive tab > Send/Receive Groups > Define Send/Receive Groups.
- Select your account and click Edit.
- Uncheck all folders except Inbox and Sent Items under the account settings.
- Set the schedule to send/receive every 5 minutes instead of every 1 minute.
- Click OK and restart Outlook.
This reduces the chance of Outlook sending multiple copies during sync.
Disable Problematic Add-Ins
Add-ins are small programs that extend Outlook’s functionality, but they can also cause chaos. Antivirus add-ins, in particular, are known to interfere with email sending.
How To Disable Add-Ins Safely
- Go to File > Options > Add-ins.
- At the bottom, next to Manage, select COM Add-ins and click Go.
- Uncheck all add-ins except those from Microsoft (like OneNote or Teams).
- Click OK and restart Outlook.
If the duplicates stop, re-enable add-ins one by one to identify the culprit.
Run Outlook In Safe Mode
Safe mode starts Outlook without any add-ins, helping you isolate the issue. If duplicates stop in safe mode, an add-in is the problem.
How To Start Outlook In Safe Mode
- Press Windows Key + R, type outlook /safe, and press Enter.
- If prompted, select your profile and click OK.
- Send a test email. If no duplicates appear, disable all add-ins as described above.
This step is quick and often reveals the root cause.
Delete And Recreate The Outlook Profile
A corrupted profile can cause all sorts of weird behavior, including duplicate sending. Creating a fresh profile is a reliable fix.
Steps To Create A New Profile
- Close Outlook and go to Control Panel > Mail (search for “Mail” in the search bar).
- Click Show Profiles > Add.
- Give the profile a name (e.g., “New Profile”) and enter your email credentials.
- Set the new profile as default by selecting Always use this profile.
- Open Outlook with the new profile and check if duplicates stop.
If they do, your old profile was corrupted. You can delete it later from the same menu.
Check For Server-Side Rules
Rules set in your email server (like Exchange or Office 365) can forward or copy messages, making it seem like Outlook is sending duplicates. This is especially common if you use a forwarding rule.
How To Review Rules In Outlook
- Go to File > Manage Rules & Alerts.
- Look for any rule that says “forward” or “copy” for sent items.
- Disable or delete any suspicious rules.
- Test by sending an email to yourself.
Also check your webmail settings—rules set there can override Outlook.
Repair Or Rebuild The OST File
An OST file stores offline copies of your mailbox. If it becomes corrupted, Outlook may send duplicates during sync. Rebuilding it is straightforward.
Steps To Rebuild OST File
- Close Outlook and open Control Panel > Mail.
- Click Email Accounts > select your account > Change.
- Under Offline Settings, uncheck Use Cached Exchange Mode.
- Click Next and then Finish.
- Restart Outlook, then re-enable Cached Exchange Mode from the same menu.
This forces Outlook to create a new OST file, often fixing sync issues.
Update Outlook To The Latest Version
Microsoft regularly releases patches for bugs, including those that cause duplicate emails. An outdated version may have known issues.
How To Update Outlook
- Go to File > Office Account > Update Options > Update Now.
- Wait for the update to download and install, then restart Outlook.
This is a simple step that many overlook.
Disable Automatic Send/Receive On Startup
Outlook’s automatic send/receive feature can trigger duplicate sends if the server is slow. Disabling it temporarily helps diagnose the issue.
How To Disable Automatic Send/Receive
- Go to Send/Receive tab > Send/Receive Groups > Define Send/Receive Groups.
- Uncheck Perform an automatic send/receive when exiting.
- Also uncheck Schedule an automatic send/receive every X minutes.
- Click OK and restart Outlook.
Now manually send/receive by pressing F9 to see if duplicates still occur.
Check For Conflicting Email Clients
If you use Outlook on multiple devices (phone, tablet, another computer), they may compete to send the same message. This is common with IMAP accounts.
What To Do
- On your phone, disable email sync for the account temporarily.
- On other computers, close Outlook and see if duplicates stop.
- If they do, reconfigure the other clients to use a longer sync interval.
This prevents multiple devices from sending the same email.
Use The Inbox Repair Tool
Microsoft includes a tool called Scanpst.exe that repairs corrupted PST files (used by POP3 accounts). This can fix duplicate issues.
How To Run Scanpst.exe
- Close Outlook and search for Scanpst.exe in your Office installation folder (usually
C:\Program Files\Microsoft Office\root\Office16). - Open the tool and browse to your PST file (found in
C:\Users\YourName\AppData\Local\Microsoft\Outlook). - Click Start and let it scan and repair any errors.
- Restart Outlook and test.
This tool is underutilized but very effective.
Reset The Outlook View
Sometimes a corrupted view setting makes it appear that duplicates exist when they don’t. This is a quick check.
How To Reset View
- In Outlook, go to the Sent Items folder.
- Click View tab > Reset View.
- Confirm and see if the duplicates disappear.
If they do, the issue was just visual, not actual duplicate sending.
Contact Your IT Administrator
If you use a corporate Exchange account, your IT admin may have set server-side rules or policies that cause duplicates. They can check the server logs for errors.
What To Ask
- Ask them to verify if there are any transport rules that forward sent items.
- Request a check for mailbox corruption on the server side.
- Inquire about recent changes to the email system.
This is especially important if none of the above steps work.
Frequently Asked Questions
Why Does Outlook Send The Same Email Twice To The Same Recipient?
This often happens due to multiple accounts configured in Outlook, a corrupted send/receive setting, or a bug in an add-in. Start by checking for duplicate accounts and disabling add-ins.
Can A Virus Cause Outlook To Send Duplicate Emails?
Yes, malware can interfere with email clients. Run a full antivirus scan if you suspect this, but most duplicate issues are caused by settings, not viruses.
Does Using Cached Exchange Mode Cause Duplicate Emails?
Rarely, but a corrupted OST file from Cached Exchange Mode can lead to duplicates. Rebuilding the OST file usually fixes this.
How Do I Stop Outlook From Sending Duplicates When Using IMAP?
IMAP accounts sync across devices. Ensure only one device sends emails at a time, and disable automatic send/receive on all but one client.
Will Reinstalling Outlook Fix Duplicate Email Issues?
It can, but it is a last resort. Try the steps above first—they are less disruptive and often solve the problem without a full reinstall.
Duplicate emails in Outlook are annoying but fixable. By working through these steps—starting with the simplest checks like duplicate accounts and add-ins—you can resolve the issue quickly. Remember to test after each change to pinpoint the exact cause. If nothing works, a fresh Outlook profile or contacting your IT admin should clear things up. You now have the tools to stop wondering “why is my outlook sending duplicate emails” and start enjoying a clutter-free inbox.