smtp;450 4.7.3 Organization queue quota exceeded. [outlook.com]
The recipient's mailbox is temporarily full. The retry may succeed once they free up space; nothing to change on your end.
Email provider · 4.x.x transient failure
Outlook SMTP 450 Errors: Every Bounce Response Explained
Every SMTP 450 response on record from Outlook (hotmail.com, outlook.com, msn.com, live.com), with the verbatim text, the enhanced status code, a severity rating and a plain-English fix.
The requested action did not happen because the mailbox was briefly unavailable, for example locked, busy, or lightly rate limited. The sending server keeps the message queued and retries it.
- Provider
- Outlook
- Code
- 450 (4xx)
- Responses
- 1
- Highest severity
- Medium
Outlook SMTP 450 responses
Outlook SMTP 450 questions
›What does an SMTP 450 error from Outlook mean?
The requested action did not happen because the mailbox was briefly unavailable, for example locked, busy, or lightly rate limited. The sending server keeps the message queued and retries it. At Outlook, it is a temporary deferral that is retried automatically, and the specific reason is in the enhanced status code and message text of each response below.
›How do I stop Outlook from returning SMTP 450?
Match your bounce text to one of the responses below and follow its guidance. Recipient-side wording means fix the address. Authentication or reputation wording (SPF, DKIM, DMARC, blocklist) means fix your sending setup, and check Outlook's postmaster documentation.