smtp;452 4.3.1 Insufficient system resources (TSTE) [outlook.com]
The receiver deferred the message and points at a mail-system problem on the receiving side (enhanced status 4.3.1). Use the wording above to pin down the exact fix.
Email provider · 4.x.x transient failure
Outlook SMTP 452 Errors: Every Bounce Response Explained
Every SMTP 452 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 action failed because the server is short on a resource, typically storage or the number of recipients it will take in one session. Sending fewer recipients per message, or simply retrying later, usually works.
- Provider
- Outlook
- Code
- 452 (4xx)
- Responses
- 1
- Highest severity
- Low
Outlook SMTP 452 responses
Outlook SMTP 452 questions
›What does an SMTP 452 error from Outlook mean?
The action failed because the server is short on a resource, typically storage or the number of recipients it will take in one session. Sending fewer recipients per message, or simply retrying later, usually works. 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 452?
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.