Hi Nihou,
What type of email is setup in Outlook (POP3, IMAP, or Exchange account)? What's your detailed Outlook version on Windows? Please click File > Account > About Outlook to collect the detailed version number.
Please try the following method to start Outlook:
Press Win+R to open Run in Windows, type Outlook /resetnavpane, press Enter. Confirm if the Outbox folder is listed there.
When the message sending issue occurred, please go to Send/Receive tab, click
Send/Receive All folders to confirm if the emails can be sent out or there is any error when sending.
If the issue persists, I suggest we can try to create a new Outlook profile: Go to Control Panel >
Mail > Show Profiles > Add, then setup this problematic account in new profile. Set "When starting Microsoft Outlook, use this profile: Prompt for a profile to be used". Use
this new profile and confirm if the issue can be fixed.
Regards,
Winnie Liang
Please remember to
mark the replies as answers if they help.
If you have feedback for TechNet Subscriber Support, contact
tnmff@microsoft.com.