What the bounce says
Exact wording as it appears in the rejection or NDR. Placeholders such as x.x.x.x and example.com stand for your own address and domain.
550 5.2.2 STOREDRV.Deliver; mailbox full The recipient's mailbox is full and can't accept messages now.
The recipient has no room. Exchange enforces a prohibit-receive quota, and once a mailbox crosses it, inbound mail is rejected with this code until space is freed or the quota is raised. Nothing on the sending side changes the outcome.
Most common causes
- The mailbox exceeded its prohibit-receive quota
- Large attachments or long retention filled the mailbox
- The user’s license or plan limits mailbox size
- Archive or retention policies are not moving items out
What to verify next
- Confirm the quota state with the recipient or their administrator
- The recipient must delete or archive mail, or the administrator must raise the quota
- Resend after the mailbox has space; Exchange does not queue for a full mailbox
- Consider whether the message could be sent without a large attachment
Quota mechanics
Exchange Online mailboxes have warning, prohibit-send and prohibit-receive thresholds. At prohibit-receive, delivery is refused. Large attachments, years of retention with no archive, and shared mailboxes that everyone uses as a filing cabinet are the common ways to get there.
The rejection is immediate and permanent for that attempt; Exchange does not queue mail for a full mailbox. Senders receive the NDR and must resend later.
- Prohibit-receive quota reached.
- No queuing; resend after space is freed.
- Archiving and retention policies prevent recurrence.
What the recipient must do
Delete or archive mail, empty Deleted Items and Recoverable Items if they count toward the quota, or have an administrator enable an online archive and raise the quota within the plan’s limits.
If the mailbox is shared and unlicensed, its quota is small; licensing it raises the limit substantially.
As a sender
Contact the recipient another way. If the message is important and large, send it without the attachment and share the file through a link so it fits once space is available.
Best diagnostic path
Mail Failure Doctor
Classify the complete rejection and preserve provider-specific diagnostic context.
Open analysis → Live analysisEmail Infrastructure Digital Twin
Map the domain’s public mail infrastructure and provider relationships before remediation.
Open analysis →Known limits
- Only the recipient or their administrator can free space or change quotas.
- Quota values depend on the recipient’s plan.
Common questions
Will the message be delivered automatically later?
No. It was rejected. Resend after the recipient has space.
Does the sender’s attachment size matter?
Only in that a smaller message may fit once a little space is freed. The quota is the recipient’s.
What about 452 4.2.2?
That is a temporary form used by some systems; Exchange Online uses the permanent 5.2.2.
Why the exact message matters
The same status family can be triggered by different conditions, and providers frequently add diagnostic text that narrows the issue. Use the complete rejection text rather than treating the numeric code as a complete diagnosis.
Provider reference
For the provider-defined meaning and current requirements, review Microsoft Exchange Online NDR reference.