421 4.7.0: try again later, closing connection
Gmail ended your session at one SMTP command and asked you to come back later, without giving a reason. It is a temporary deferral.
- Gmail
- Provider
- Temporary (4xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 421 4.7.0
- Provider
- Gmail and Google Workspace
- Temporary or permanent
- TemporaryThe sending server keeps the message and tries again later.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
421 4.7.0 Try again later, closing connection.
What it means
The reply names no cause. Gmail adds the SMTP command it was answering in brackets, such as (EHLO) or (MAIL), and closes the connection. Because the code is temporary, your server keeps the message and retries, and a one-off is nothing to worry about. When it repeats across many messages, it is generally read as Gmail slowing down a sender it does not yet trust: a new IP or domain, a sudden jump in volume, or mail that recipients mark as spam. Check Postmaster Tools, your authentication and your sending rate before raising volume again.
Common causes
- A sudden increase in volume from your IP or domain.
- A new IP or domain with little sending history at Gmail.
- A rising spam complaint rate or a weak reputation.
- Too many simultaneous connections from your servers.
How to fix it
- 01Let your server retry with increasing delays.
- 02Slow your sending to Gmail and spread it over the day, especially after a jump in volume.
- 03Check your domain and IP reputation and your spam rate in Google Postmaster Tools.
- 04Confirm that SPF, DKIM and DMARC pass and that your sending IP has a matching PTR record.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Gmail SMTP errors and codes (Google Workspace Admin Help)knowledge.workspace.google.com
Related codes
- 421 4.7.28Unusual rate of mail.Gmail saw an unusual rate of mail from you and has temporarily rate limited it, to protect its users from possible spam.
- 421Service not available.The receiving server is closing the connection and will not take mail right now. The reply is temporary, so the sending server keeps the message and tries again later.
- 5.7.0Security or policy refusal, unspecified.The message or session was refused for a security or policy reason that the server did not describe more precisely, or chose not to reveal.
Further reading
All 108 Gmail codesEvery code in the wikiPaste your own bounce