Sending, receiving, and organizing email in Outlook.com
Hi, I'm John! I will help you with this.
I understand the confusion. Microsoft 365 does include extra storage, but Outlook mailbox storage and OneDrive storage are counted separately.
Your Outlook.com mailbox has its own storage limit. If it is full, you may not be able to send or receive emails even if your Microsoft 365 subscription is active.
Please check your mailbox storage here: https://outlook.live.com/mail/0/options/general/storage
Also check your Microsoft account storage here: https://account.microsoft.com/storage
Please also make sure you are signed in to Outlook.com using the same Microsoft account that has the Microsoft 365 subscription.
If you recently renewed, upgraded, or bought Microsoft 365, the storage change may take up to 24 hours to sync properly everywhere.
Let me know what you find. Thanks!