450 4.7.1: Temporarily refused, often greylisting
The server refused the first attempt on purpose. Real mail servers wait a few minutes and retry, and the second attempt gets through. Spam software often doesn't retry.
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:
450 4.7.1 <[email protected]>: Recipient address rejected: Greylisted, see http://postgrey.schweikert.ch/help/example.com.html451 4.7.1 Please try again laterCommon causes
- Greylisting on the receiving server
- Temporary rate limits
How to fix it if you sent the email
- Usually nothing. Your server will retry within minutes and the message will be delivered.
- If it still fails after a day, check the full bounce for a 5.x.x code.
If you manage the receiving or sending mail system
- If you send from many IP addresses, retries may come from a different one; most greylisting systems handle this, but you can ask the receiver to allow your range.
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 450 4.7.1 mean?
- The server refused the first attempt on purpose. Real mail servers wait a few minutes and retry, and the second attempt gets through. Spam software often doesn't retry.
- Is 450 4.7.1 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 4.7.1 bounce?
- Not straight away. Retry later, and remove it only if it keeps failing for weeks.