Email provider
Zoho SMTP Error Codes and Bounce Messages
Zoho Mail is the mail product inside Zoho's business software suite, with its own spam filtering, firewall and blocklist controls.
- Codes on record
- 6
- Responses
- 10
- Domains
- zoho.com
Postmaster & documentation
SMTP 4511 response
A temporary problem. The sending server keeps retrying for a while, and delivery often recovers on its own once the underlying issue clears. See SMTP 451 across every provider
SMTP 4522 responses
A temporary problem. The sending server keeps retrying for a while, and delivery often recovers on its own once the underlying issue clears. See SMTP 452 across every provider
SMTP 5502 responses
A hard failure. The receiving server has refused the message for good and will not accept an unchanged retry without a change on the sending side. See SMTP 550 across every provider
SMTP 5522 responses
A hard failure. The receiving server has refused the message for good and will not accept an unchanged retry without a change on the sending side. See SMTP 552 across every provider
SMTP 5531 response
A hard failure. The receiving server has refused the message for good and will not accept an unchanged retry without a change on the sending side. See SMTP 553 across every provider
SMTP 5542 responses
A hard failure. The receiving server has refused the message for good and will not accept an unchanged retry without a change on the sending side. See SMTP 554 across every provider
Zoho bounce questions
›Why is Zoho bouncing my email?
Zoho Mail is the mail product inside Zoho's business software suite, with its own spam filtering, firewall and blocklist controls. Match the exact wording of your bounce to one of the 10 responses on this page to find the specific reason and fix.
›How do I improve deliverability to Zoho?
Authenticate with SPF, DKIM and DMARC, keep your sending IP and domain reputation clean, mail only engaged recipients, and honour unsubscribes. Zoho also publishes postmaster guidance, linked on this page.
