421 4.7.28: Unusual rate of unsolicited email (Gmail)
Gmail is slowing down mail from your IP address or domain because a lot of it looks like spam to Gmail users.
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:
421-4.7.28 Gmail has detected an unusual rate of unsolicited email originating from your IP address. To protect our users from spam, mail sent from your IP address has been temporarily rate limited.Common causes
- High spam complaint rates
- A sudden jump in volume
- Sending to old or bought lists
- A hacked account or website sending spam
How to fix it if you sent the email
- Slow down and send only to people who asked for your email.
- Check your spam rate in Google Postmaster Tools.
- Clean your list. See how to clean an email list.
If you manage the receiving or sending mail system
- Look 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 4.7.28 mean?
- Gmail is slowing down mail from your IP address or domain because a lot of it looks like spam to Gmail users.
- Is 421 4.7.28 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 4.7.28 bounce?
- Not straight away. Retry later, and remove it only if it keeps failing for weeks.