Hello Jukka Koti,
I'm sorry to hear that you're having trouble sending and replying to emails. I know how frustrating it is when your inbox suddenly stops working right when you need it.
Since a little time has passed, may I know if you've been able to send and receive normally again, or is the issue still happening? If you are still unable to send emails, let's run through a few quick troubleshooting steps to isolate the problem:
Step 1: Send a test email via the web
Please log into Outlook on the web using a browser. Try sending a quick test email to yourself to see if it goes through.
Step 2: Check your storage
If the test email fails to send, please check both of your storage limits (Microsoft Storage and Email Storage) to ensure neither is full. You can do this in Outlook Web by clicking the Settings (gear icon) at the top right > General > Storage.
If your storage has plenty of free space but emails are still failing, do you receive any specific error messages or "undeliverable" bounce-back emails? If you are seeing an error message, please share the exact text or code it gives you here.
If you have any other questions or need further assistance, please feel free to reach back out.
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