421 4.7.0: Temporarily deferred: try again later
The receiver is slowing you down. Your server will keep retrying, but if it continues, mail can be delayed for hours and eventually bounce.
Temporary Often fixes itself or after a small change. Your server may retry.
What the bounce message looks like
The wording changes from one provider to another. These are typical examples:
421 4.7.0 Try again later, closing connection. (Gmail)421 4.7.0 This message is suspicious due to the very low reputation of the sending IP address. (Gmail)421 4.7.28 Gmail has detected an unusual rate of unsolicited email originating from your IP address. (Gmail's related rate-limit code)Common causes
- Sending too many messages too quickly
- A sudden jump in volume from a new domain or IP
- Many spam complaints or bounces
How to fix it if you sent the email
- Send in smaller batches, spread over time. See how many emails per day.
- Clean your list so fewer messages bounce. See how to clean an email list.
- Check your authentication with the DMARC checker.
If you manage the receiving or sending mail system
- Lower the sending rate and check for compromised accounts or scripts sending spam.
Free tool: paste the full bounce into the bounce message decoder to get a plain-English reading of every code in it.
Questions people ask
- What does 421 4.7.0 mean?
- The receiver is slowing you down. Your server will keep retrying, but if it continues, mail can be delayed for hours and eventually bounce.
- Is 421 4.7.0 a hard or soft bounce?
- Temporary. Often fixes itself or after a small change. Your server may retry.
- Should I remove the address after a 4.7.0 bounce?
- Not straight away. Retry later, and remove it only if it keeps failing for weeks.