550: rejected as spoofed
The recipient’s Barracuda gateway decided your message pretends to come from a sender it does not really come from, and refused it.
- Barracuda
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- Either side, depending on the cause. Start with the checks below that are yours.
- What the server says
550 Rejecting spoofed message.
What it means
Barracuda gateways have protections against spoofing, where a message claims a sender address it is not entitled to use, for example one at the recipient company’s own domain. This reply is the permanent rejection when those protections match. Legitimate mail falls into it when a third party sends using another organisation’s domain, or when authentication for the From domain fails. The documentation lists the reply without detail on which check produced it, so the recipient’s administrators are the ones who can see the exact reason in their message log.
Common causes
- Your message uses the recipient company’s own domain in the From address while coming from outside.
- A service sends on behalf of a domain without being authorised by that domain’s SPF, DKIM or DMARC.
- Forwarding that breaks authentication for the original sender.
How to fix it
- 01Check the From address your message used and whether that domain authorises your server.
- 02Send from your own domain with SPF, DKIM and DMARC passing.
- 03If you send for the recipient company, ask their IT team to allow your sending IPs on their Barracuda gateway.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- SMTP Error Codes, Barracuda Email Security Gateway documentationdocumentation.campus.barracuda.com
Related codes
- 550Mailbox unavailable.The receiving server permanently refused the message for this recipient: the mailbox does not exist, cannot be reached, or the server rejected the message by policy.
- 550SPF check failed.The recipient’s Barracuda gateway checked the SPF record of your sending domain, found your server not authorised, and rejected the message.
550 at other providers
- 550 [SC-001]Outlook.com policy block for content or reputation.Outlook.com rejected the mail for policy reasons tied to spam-like content or to the reputation of the sending IP or domain.
- 550 [SC-002]Outlook.com block for namespace mining.Outlook.com blocked the sending IP because it behaved like a namespace miner, checking whether addresses exist without sending mail.
- 550 [SC-003]Outlook.com block for an open proxy or relay.Outlook.com rejected the mail because the sending IP appears to be an open proxy or open relay.
- 550 [SC-004]Outlook.com block after complaints.Outlook.com placed a block on the sending IP because it received complaints about mail coming from it.
- 550 [DY-001]Outlook.com refuses dynamic IP addresses.Outlook.com rejected the mail because the sending IP is dynamic address space, which it generally does not accept mail from.
- 550 [DY-002]Outlook.com block for a likely compromised sender.Outlook.com rejected the mail because the sending server or computer appears to be compromised or infected.
Further reading
All 11 Barracuda codesEvery code in the wikiPaste your own bounce