SMTP 554 5.7.1 Blocklisted: Find the List and Get Delisted

A 554 5.7.1 reply that names a list means the receiving server looked up your sending IP address (or sometimes your domain) in a blocklist, found it, and refused the connection or message. A typical bounce reads:

554 5.7.1 Service unavailable; Client host [203.0.113.7] blocked using zen.spamhaus.org; https://www.spamhaus.org/query/ip/203.0.113.7

The text after the semicolon is the useful part. It names the list (here, Spamhaus ZEN) and often links to a lookup page. A 5.7.1 reply with no list name is a policy rejection of another kind; see SMTP 550 5.7.1 message rejected.

Step 1: confirm which IP is listed

Find the IP your mail actually leaves from. It may differ from your website's IP, especially with a relay, a shared host or a cloud provider. Read the Received headers of a bounced message, or your mail log, then check it with the What Is My IP tool from the sending server.

Run the address through the Blacklist Checker. It tests many DNS-based blocklists at once. A single minor list is rarely the cause of every bounce; the list named in your actual bounce is the one that matters.

You can also query a list by hand. DNSBLs work by reversing the octets of the IP and looking up a name under the list's zone:

## Checking 203.0.113.7 against a DNSBL zone
dig +short 7.113.0.203.zen.spamhaus.org A

An answer in 127.0.0.x means listed, and no answer means not listed. Some lists refuse queries sent through large public resolvers, so a non-answer through 8.8.8.8 is not proof. Use your own resolver or the list operator's web lookup. The glossary entry on DNSBL explains the mechanism.

Step 2: work out why you were listed

Delisting without a fix gets you relisted within days. The usual causes, in order:

1. A compromised account or website. A hacked contact form, script or mailbox sending spam. Check the mail queue (mailq on Postfix) for thousands of messages you did not write.
2. A shared or recycled IP. On shared hosting or a new VPS, the address may carry a previous tenant's reputation. Ask the provider for a different IP.
3. A dynamic or residential range. Lists such as Spamhaus PBL cover address space that should not send mail directly. This is a policy listing, not misbehavior. Send through your provider's authenticated relay instead.
4. Missing basics. No reverse DNS, a mismatched HELO name, or no SPF. See reverse DNS for email.
5. Bulk sending to stale lists. High bounce or complaint rates from an unconfirmed list.

If an account is compromised, clean it first: reset passwords, remove the malicious script, update the CMS and plugins. Our WordPress site hacked recovery covers the website side.

Step 3: request delisting

Each list runs its own process. Follow the link in the bounce or go to the list operator's own site, never a third-party "removal service" that asks for payment. General points:

• Many lists only accept removal once the cause is fixed, and some expire entries automatically after a quiet period.
• Policy-based listings (dynamic ranges) are removed by the IP owner, usually your ISP or host, not by you.
• Some operators ask you to explain what was fixed. Be specific and brief.
• Allow time. Removals vary from automatic and near-instant to a day or more, depending on the list.

Our email blacklist removal guide walks through the process for the major lists.

Step 4: keep it from happening again

• Publish SPF, DKIM and DMARC and check them with the Email DNS Checker.
• Set a PTR record that matches your HELO name and forward DNS.
• Rate-limit outgoing mail per account and alert on queue growth.
• Send bulk or transactional mail through a reputable provider with a dedicated or well-managed IP, and warm up new addresses (email warmup for a new domain).

Verify

After delisting, wait a few minutes for caches to expire, then rerun the Blacklist Checker and send a test through the Email Deliverability Test. Watch the bounce rate over the next day.

Next steps

• Use the Blacklist Checker on your sending IP.
• Follow the email blacklist removal guide.
• Fix mail going to spam with email going to spam fix.
• Set up reverse DNS using reverse DNS for email.

FAQ

Does a blocklisting mean my domain is blocked everywhere?

No. Each receiver decides which lists to consult. You may bounce at one provider and deliver normally to another.

Can I fix it by changing my sending address?

Changing the From address does nothing for an IP listing. The receiver blocked the connecting IP, so the fix is to clean up and delist that IP or move to another.

How long does delisting take?

It depends on the list. Some remove entries automatically after a period without abuse, others review requests manually. Check the operator's page for current wording.

Is it safe to pay a delisting service?

Legitimate major lists do not charge to remove standard listings. Use the operator's own site and be cautious of any intermediary asking for money.

This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.