Hi @Eugenie van Leeuwen Good afternoon and thank you for your question. Before we get started, please remove the email address on your question due to security and PII reasons.
First, can we please know if you're using personal or work/school account?
If personal account, please check the following:
- Inbox rules
- Mailbox storage (if full)
If work/school account, please work with your admin to do the following:
- Message trace
- Check transport rule (ETR)
- Check inbox rule
- Check tenant allow/block rule
I also suggest posting your question at the following: https://learn.microsoft.com/en-us/answers/tags/337/office-exchange-online-management https://support.microsoft.com/en-us/office/get-help-with-outlook-com-40676ad0-c831-45ac-a023-5be633be798d
I hope I was able to assist you on your question. If yes, please Upvote this and Accept it as the answer.
Have a great day ahead!