Microsoft documents one cause of duplicate sent messages in Outlook for Windows. IMAP accounts get a copy from the mail server and a second copy from Outlook. One copy shows as unread. One setting stops the second copy. Microsoft lists no fix date.
Your Sent Items folder shows the same message twice and one copy is unread. Microsoft lists this as a known issue for IMAP accounts.
Facts follow the Microsoft Support known issue page on IMAP sent messages duplicated and unread in Sent Items. Microsoft names Outlook for Microsoft 365, Outlook 2024, Outlook 2021 and Outlook 2019 for Windows.
What Causes Duplicate Sent Messages?
Mail servers create a Sent Items copy on their own. Outlook then uploads the same message again. Outlook takes the unread flag from the server. Copies marked unread there show as unread in Outlook. Microsoft names Gmail, AOL and Yahoo among the affected providers.
How to Stop the Duplicate Copies?
- Select File, Account Settings and Account Settings.
- Select your IMAP account and then Change.
- Tick the box that stops saving copies of sent items.
- Select Next and then Done.
Microsoft calls this a workaround. Neither a fix nor a timeline appears on the page. Some providers also drop BCC recipients from Sent Items. That problem depends on the provider so the workaround can fail there.
What About Duplicates From Imports?
Microsoft ties duplicate calendar items to the Allow duplicates to be created option in the Import and Export Wizard. See how to delete duplicate calendar entries in Outlook for the steps.
What does Microsoft Not Say?
Microsoft explains duplicate sent messages only on that page. Duplicate received messages get no cause or fix there. Older posts list other causes for those. Microsoft gives none on this page.
Related reading: how to solve a full mailbox in Outlook and how to reduce the size of an Outlook data file.
Frequently Asked Questions
Why are Sent Messages Duplicated in Outlook?
Mail servers create a Sent Items copy and Outlook uploads the same message again. Microsoft documents this for IMAP accounts.
Which Providers are Affected?
Microsoft names Gmail, AOL and Yahoo among others.
How do I Stop Duplicate Sent Items?
Open the IMAP account settings and tick the box that stops saving copies of sent items.
Is There a Fix From Microsoft?
No. Microsoft lists the issue as known and gives a workaround with no fix timeline.
Key Takeaways
- IMAP accounts store two sent copies when the server and Outlook both save one.
- Outlook shows the unread flag from the server.
- One account setting stops the second copy.
- Microsoft gives no fix date.
- Microsoft explains sent messages and not received messages here.
Sources and References
Facts follow Microsoft Support.
- IMAP sent messages duplicated and unread in Sent Items (Microsoft Support) support.microsoft.com