Email provider · 4.x.x transient failure
Every SMTP 452 response on record from Zoho (zoho.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.
smtp;452 <[email protected]> Mailbox delivery restricted by policy error
The receiver deferred this message and will retry it automatically. A failure that sticks around usually traces back to rate limits, reputation, or a policy on the receiving side.
smtp;452 4.3.1 Temporary System Error
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.
Postmaster & documentation
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 Zoho, 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.
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 Zoho's postmaster documentation.
