Hello Paul Casey2,
Thank you for posting this case in Microsoft Community!
Based on your description: Why are Sent emails being marked Draft in the sent folder and also in the Draft folder? I would like to cooperate with you working on this case. To clarify this case, would you please help to collect following information for further investigation?
- Are you using New Outlook for WindowsorClassic Outlook for Windows?
- Are you usingMicrosoft 365 ora Business account(@xxx.onmicrosoft.com/@domain.com)?
- Or using personal account type such as Outlook.com, Hotmail.com, Live.comand so on? Or using other third-partyPOP/IMAPaccount?
- Have you tried to sign in Outlook Web and check if getting the same case?
- How about your Outlook version? Please kindly provide us your Outlook version with product details by going to New Outlook>Settings>General>About Outlook or Classic Outlook>File>Office Account and share that entire page screenshot with hide personal information. What version of Outlook do I have?
For my suggestion, you may check following workaround to narrow down this issue:
- Firstly, you may check if there is any specific rule which moved the sent emails to the Draft folder. If using New Outlook, please if you have the "Undo send" setting enabled.
This setting makes it so that every email you send goes into the Drafts folder, then it automatically sends after a few seconds. The purpose of it is to give you a chance to edit it or delete it before it actually goes to the recipient. But it should only show up in the Drafts folder first and then only in the Sent folder, so if you're seeing a copy in both folders at the same time and it stays in the Drafts folder, then it's probably not because of that setting. You may go to View > View Settings > Mail > Compose and reply > Undo sendand check if set up 10 minutes. If Yes, you may change it to 0 minutes to avoid this case.

By the way, you may also sign in Outlook Web and go to View > View Settings > Mail > Compose and reply > Undo sendand check and check if the same settings enabled as well.
- Next, you may try to go to Settings>Accounts>Email Accountsand find your account to clickManageoptions. Then you can click Removeyour account profile and Add an email account to Outlook for Windows - Microsoft Support to check again.
- If this case still persists, you may check this article as reference Troubleshooting Outlook for Windows issues and perform all the steps completely.
- If using Classic Outlook, you may go to File > Options > Mail > Save messagesand check if below settings enabled or not. If Yes, please disable the options to avoid this case.

Hope the above workaround would be helpful. If you need further assistance, please feel free to let me know, I will keep assisting you.
Your understanding and patience will be appreciated.
Thank you!