Outlook mails are blocked - not enough space

This looks like a stuck mailbox quota, so go to Outlook on the web, open Settings then General then Storage, delete a few emails again, then fully empty Deleted Items and Junk, sign out everywhere, then sign back in and wait up to 24 hours.

Hi,

Are you checking your mailbox storage inside Outlook.com settings or only your OneDrive storage?

Your issue comes from mailbox quota, not OneDrive. Outlook counts emails, attachments, and hidden folders like Deleted and Junk. If it shows 37 GB on a 5 GB limit, your mailbox is over limit or stuck in sync. Go to Settings, then Storage, delete large emails, then empty Deleted and Junk folders.

After cleanup, wait for the storage to refresh.

The mailbox is blocked because Microsoft cloud storage is treated as over quota, even though OneDrive appears to have free space. When Microsoft storage or email storage is exceeded, Outlook.com blocks sending and receiving mail until the account is back under quota.

Key points from the storage behavior:

• If Microsoft cloud storage is full ("Microsoft Unified Storage is full" / storage quota exceeded):
  • Cannot send or receive email in Outlook.com, even if email storage itself is not full.
  • Messages sent during this time are bounced and unrecoverable.
• If only email storage is exceeded:
  • Cannot send or receive email in Outlook.com.
  • Messages sent to the mailbox are returned to the sender and must be resent after freeing space.

To restore mail flow, the account must be brought back under the Microsoft storage quota, not just under the visible OneDrive 5 GB:

1. Check actual Microsoft storage status
   • Use the mailbox storage page referenced in the Outlook.com article to see what is consuming space in Microsoft storage (OneDrive, Outlook.com mail, and other services together), not just the OneDrive web view.
2. Free up storage or buy more
   • If using the free tier, either:
     • Buy a subscription or buy more storage, or
     • Delete content until the total Microsoft storage is below the quota. This can include:
       • Large or unnecessary files in OneDrive (use the "view the largest files" tool: https://go.microsoft.com/fwlink/?linkid=859455).
       • Old or large emails and attachments in Outlook.com.
       • Content in other Microsoft services that contributes to storage (for example, Loop workspaces or Designer projects, as described in the storage quota article).
3. Wait for the quota state to refresh
   • After freeing space or purchasing additional storage, allow time for the quota status to update. Once the account is under quota, Outlook.com will resume sending and receiving mail. Any messages bounced while over quota must be resent by the senders.

If the storage page still shows an incorrect over‑quota value after cleaning up and/or purchasing storage, the issue is account‑specific and requires Microsoft support intervention. For a consumer Outlook.com account, use the support entry points in Outlook.com (Help → Contact support) or the Microsoft account help channels to open a ticket, referencing that Microsoft storage is reporting over quota and blocking Outlook.com mail despite visible free space in OneDrive.

References:

• Storage limits in Outlook.com
• Can't send or receive email in Outlook.com
• Microsoft storage quotas
• storage exceeded in outlook after purchasing MS 365 subscription - Microsoft Q&A
• Reminder: Microsoft storage limit exceeded - Microsoft Q&A