550: message detected as spam
The Free antispam filter judged the message to be spam and refused it on arrival. Free has a false positive procedure for legitimate mail.
- Free
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550
- Provider
- Free (free.fr)
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
550 spam detected
What it means
Free filters mail for free.fr addresses, and the same reply appears on mail sent through its own servers. A 550 spam detected means the filter analysed the message as spam and refused it at reception. If you did not send the message, the bounce came from a server that relayed spam using your address. If you did, Free asks you to check the message first: run it through antispam software, make sure it is syntactically correct, and avoid techniques spammers use. For a genuine false positive, Free wants a near-identical copy so it can reproduce the problem.
Common causes
- The content, links or structure of the message look like spam to the filter.
- The message is malformed, with inconsistent headers or a wrong declared encoding.
- Someone sent spam with your address as the sender, and the bounce came back to you.
How to fix it
- 01Check the message with antispam software and fix syntax or encoding problems.
- 02Make sure the message follows the RFCs and avoids techniques common to spam.
- 03For a false positive, resend the same message with the same tools and servers to nospam@nospam.proxad.net (as a blind copy alongside the original recipients if possible).
- 04Then write to postmaster@proxad.net giving the sender, the subject and the error message as text.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- postmaster.free.fr (Free)postmaster.free.fr
Related codes
- Too many spams from your IP.Your server sent too much spam to Free subscribers, so Free stopped accepting its connections for up to 24 hours. The page does not settle which reply code comes with it.
- 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.
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.