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Undeliverable mail

Your email came back. Here is what that actually means

Forward the undeliverable notice and we will tell you, in plain words, whether the address is wrong or something is blocking your mail. Those are very different problems and the bounce message never says which.

Works on Microsoft, Google, and any standard delivery report. Forward the whole thing, not a screenshot.
Bounce Checker · undeliverable notice
The address was fine. Microsoft blocked YOU.
Nothing is wrong with who you emailed. Microsoft decided not to accept mail coming from your domain, because it could not confirm the message genuinely came from you.
WHOSE PROBLEM
Yours to fix: your SPF record, so it lists the server you actually send from.
TRY AGAIN?
No, not until you fix that record. Resending before then fails identically every time, because SPF is the published list of servers allowed to send as you, and the one that sent this was not on it.
Technical detail: 5.7.26 · permanent · refused by outlook.com
Example. Yours runs on the actual notice you forward.

What you get

The parts that matter, without the marketing.

Tells you whose problem it is

The one thing the bounce never says. A wrong address and a blocked sender look identical to you and are fixed in completely different ways.

No codes to look up

“550 5.7.26” becomes “the receiving server could not confirm the mail came from you.” The code is still there if you want it.

Says whether to try again

Some failures clear on their own within hours. Others will fail identically forever, and resending damages your reputation.

How it works

Three steps. Nothing to install.

1

Forward the whole notice

The useful part is usually near the bottom under a heading like technical details, so send the full message rather than a screenshot.

2

Get it in plain words

What happened, whose end the problem is at, and whether resending would help.

3

Fix the right thing

If it is the address, you need a different one. If it is you, we point at the exact record to fix.

Have an email that bounced right now?

Forward the undeliverable notice to this address and we will reply with a plain-English report. Free, no account needed. The same address takes suspicious emails too; we work out which one you sent.

scan@inbox.mailarrive.com

Forwarded messages are analyzed, kept 30 days, then deleted.

Common questions.
What does it mean when an email bounces?

It means a mail server refused to deliver your message and sent you a notice explaining why. The notice always contains a short code giving the reason, but almost never explains it in words. The two things worth knowing are whether the failure is permanent and whether the problem is the address you wrote to or your own sending setup.

What does 550 5.1.1 mean?

The mailbox does not exist. The company's mail server is working fine, it just has no account with that name, so it is usually a typo or somebody who has left. No amount of changing your email settings will fix it; you need a different address.

What does 550 5.7.26 mean?

The receiving server could not confirm the message genuinely came from your domain, so it refused it. The address you wrote to was fine. This is an authentication problem on your side, normally SPF, DKIM or DMARC, and it is fixable.

Is a bounce my fault or theirs?

It depends entirely on the code, which is why the notice is so frustrating to read. Codes in the 5.1 range are almost always the address. Codes in the 5.7 range are almost always about you, meaning your domain's authentication or reputation. Our checker tells you which without you having to learn the difference.

Should I just send it again?

Only if the failure was temporary, which is anything starting with a 4. Those retry on their own for a day or two. A permanent failure, starting with 5, will fail identically every time, and repeatedly bouncing mail at the same provider damages how they treat everything else you send.

Is it free?

Yes. A free account includes bounce checks alongside the other smart checks, with a daily limit. No card needed.

Got one sitting in your inbox right now?

Create a free account, forward the undeliverable notice to your private address, and we will read it for you.

Create a free account
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