What does a 550 email bounce error mean?
By Ash, Founder, HosteazePublished 2 min read
The short answer
A 550 error means the receiving mail server permanently refused your email, so it won't try again. The extra code after it gives the reason. 5.1.1 means the address doesn't exist, 5.7.1 means it was blocked as spam or by a policy, and 5.7.26 means your domain's SPF or DKIM authentication failed.
A bounce message full of codes is mail servers talking to each other, and they weren't written with you in mind. The good news is that the code after "550" tells you almost exactly what went wrong. You just need to know where to look.
How do I read a 550 bounce message?
Open the bounce and look for a line like this one, which is Gmail's wording:
550 5.1.1 The email account that you tried to reach does not exist.| Part | Meaning |
|---|---|
550 | The basic reply code: permanent refusal. |
5.1.1 | The enhanced status code, which gives the reason. |
| The text | The receiving server's explanation, which varies by provider. |
The first digit matters most. A 5 means permanent, so the sending server gives up straight away.
What do the common 550 codes mean?
| Code | What it usually means | What to do |
|---|---|---|
550 5.1.1 | The address doesn't exist | Check for typos. If it's right, the mailbox has been closed. |
550 5.2.1 | The mailbox is disabled or inactive (in Gmail's wording) | Contact the person another way. |
550 5.7.1 | Blocked by a spam filter or the recipient's policy | Check your domain and IP aren't on a blocklist, and read the text for the rule that was hit. |
550 5.7.26 | Your email failed authentication (Gmail) | Set up SPF and DKIM for your domain. |
550 5.7.515 | Your domain doesn't meet Outlook.com's authentication rules for high-volume senders | Make sure SPF, DKIM and DMARC all pass. |
Wording varies between providers, so treat the table as the common meaning, then read the text for the detail.
What if the error is about authentication?
Since February 2024, Gmail has required every sender to have at least SPF or DKIM, and it bounces unauthenticated email with 550 5.7.26. Outlook.com introduced similar rules in May 2025 for domains sending more than 5,000 emails a day. If you see either code, the fix is in your DNS, not your email. Follow how to set up SPF, DKIM and DMARC. If you use several email tools, check you haven't gone over the SPF limit, covered in fixing "too many DNS lookups".
What if only one recipient bounces?
Then it's probably their side: a closed mailbox, a typo, or a strict company filter. Send from a personal address to check the address works, or ask them to add you to their allowed senders. If lots of different recipients bounce with 5.7 codes, the problem is your domain, and it may also be why other emails are going to spam without bouncing.
Frequently asked questions
What is the difference between a 4xx and a 5xx bounce?
A code starting with 4 is temporary, so the sending server tries again later. A code starting with 5, such as 550, is permanent, and the email won't be delivered unless something changes.
Is a 550 error my fault or the recipient's?
It depends on the code. 5.1.1 usually means a mistyped or closed address on their side. 5.7.1 and 5.7.26 usually point to your domain's reputation or authentication, which is yours to fix.
Should I keep emailing an address that gave a 550 5.1.1?
No. Remove it from your lists. Repeatedly sending to addresses that don't exist damages your sending reputation with every provider.
