550: sender domain on a Spamhaus blocklist
GMX refused your mail because your envelope or From domain is listed on a Spamhaus blocklist. GMX makes no exceptions; the listing must be removed at Spamhaus.
- GMX, WEB.DE
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550
- Provider
- GMX, WEB.DE and mail.com
- 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 Reject due to policy restrictions
What it means
GMX checks sender domains against Spamhaus. In case r1102 the domain of the envelope sender (RFC 5321 MailFrom) is listed, and in case r1103 the domain of the From header (RFC 5322 From). Either way GMX rejects the mail with 550 and, as the case pages say, exceptions are not possible. Writing to GMX will not change this while the listing stands. The lookup at check.spamhaus.org shows whether the domain is still listed and how delisting works; once Spamhaus removes it, GMX accepts the mail again.
Common causes
- The domain was used in spam, by you or by someone forging it.
- The domain is newly registered or shares traits Spamhaus associates with abuse.
- Links or hosting connected with the domain were used in spam campaigns.
How to fix it
- 01Look the domain up at check.spamhaus.org to confirm the listing and its reason.
- 02Fix the cause Spamhaus gives and follow its delisting process.
- 03Protect the domain with SPF, DKIM and a DMARC policy to make forging it harder.
- 04Retry delivery once the listing is gone; GMX needs no separate request.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 550Envelope domain on a GMX blocklist.GMX refused your mail because the domain in your envelope sender (MAIL FROM) is on one of its own blocklists.
- 554IP address on a Spamhaus blocklist.GMX refused the connection because your sending IP is listed on a Spamhaus blocklist. GMX makes no exceptions; the listing has to be removed at Spamhaus.
- 554Link to a domain on the Spamhaus DBL.GMX refused the message because it links to a domain listed on the Spamhaus Domain Block List (DBL). The listing has to be resolved at Spamhaus.
- 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.
Further reading
All 57 GMX, WEB.DE codesEvery code in the wikiPaste your own bounce