Part 1 · 1.1
Error code 550: which variant do you have and what should you do?
An error code that starts with 550 means the mail has been permanently rejected. Resending only helps once the cause has been fixed. The second code after the 550, such as 5.1.1 or 5.7.1, and the text that follows it tell you why. Look up your variant below.
What the message looks like
You receive a mail back from Mail Delivery System or MAILER-DAEMON, with a subject such as Mail delivery failed: returning message to sender. It contains a line like this:
SMTP error from remote mail server after RCPT TO:<pieter@example.net>: 550 5.1.1 <pieter@example.net>: Recipient address rejected: User unknown
If it says SMTP error from remote mail server, the recipient's server rejected the mail. To learn how to read a bounce in full, see Mail delivery failed: how to read the error message and what the codes mean.
The variants
| Code or text | What does it mean? | What should you do? |
|---|---|---|
| 550 5.1.1 User unknown, Recipient address rejected, No such user | The recipient's address does not exist. | Check the spelling of the address. |
| 550 5.5.0 Requested action not taken: mailbox unavailable | The recipient's mailbox is unavailable: the address does not exist, the mailbox is full or there is a problem on the recipient's side. | Check the address and ask the recipient through another channel. In detail: Error message: 550 5.5.0 Requested action not taken: mailbox unavailable. |
| 550 5.7.1 Relaying denied | Your mail program does not log in to the outgoing server. | Turn on authentication for the outgoing server. See Relaying denied: your email program isn't logging in. |
| 550 5.7.26 (Gmail), 550 5.7.509 (Microsoft), SPF check failed, DMARC check failed | SPF, DKIM or DMARC is not set up correctly for your domain. | Set them up correctly, including for services that send mail on your behalf. See My mail ends up in the recipient's spam. |
| 550 5.7.515 (Microsoft) | You send a lot of mail to Outlook.com without passing SPF and DKIM, or without DMARC. | Set up SPF, DKIM and DMARC correctly. |
| 550 5.7.25 (Gmail) | The sending server does not have a valid reverse DNS (PTR). | With a hosting package, we take care of this. With a VPS, you do it yourself. |
| 550 5.7.606 (Microsoft), banned sending IP | Microsoft has blocked the IP address of the sending server. | If your mail goes through our server, send us the bounce. |
| 550 5.7.708 (Microsoft) | You send through Microsoft 365 and Microsoft no longer accepts traffic from that environment. | Ask the administrator of your Microsoft 365 to contact Microsoft. |
| 550 with blocked using, listed at, Spamhaus | An IP address is on a blacklist. | See Sending rejected: blacklists and limits. |
| 550 5.7.1 with a different text | The recipient rejects the mail based on their own policy, for example because they see it as spam. | Read the text: it tells you why. |
Mail to you is rejected with 550
Does someone who emails you get a 550 back? Then our server is rejecting the mail. The most common causes:
- 550 User unknown, No such user: the address does not exist on the server. Check the spelling, or create the address in DirectAdmin under E-mail Accounts. Is your mail handled by another provider, such as Microsoft 365? Then check your MX records.
- 550 with spam, blocked or policy: our spam filter or a blocklist is rejecting the sender. Ask the sender to send you the full message and contact us.
How to fix it
- Find the line in the bounce with the code and the text that follows it.
- Look up the code in the table above.
- Is it a typo in the address? Correct the address and send the mail again.
- Is it about SPF, DKIM or DMARC? Check your domain with the free Email Health Check and set the records up correctly.
- No bounce, but your mail still does not arrive? Look it up with E-mail Tracking in DirectAdmin (see E-mail Tracking: where has my mail gone?).
When should you contact us?
Does the error message contain a WebOké IP address, or a code such as 5.7.606 that relates to the IP address of the sending server? Then it is up to us.
Ask the AI assistant in My WebOké first, or create a ticket via Support centre and then Submit a ticket. Include:
- the full error message, including the line with the code (forward the mail as an attachment)
- the sender's and the recipient's address
- the date and time it was sent
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Want to learn more? The free course Getting your email in order includes Reading a bounce and Common error codes explained.