Blacklist monitoring: how to check and delist a domain or IP

Draft — written from product facts + domain knowledge; UI labels to be verified before publishing.

A blacklist (blocklist, DNSBL) is a public list of domains or IP addresses reported for sending spam. Receiving servers query these lists and reject or junk mail from anything listed. A listing can appear overnight and cut inbox placement for an entire domain. Check weekly and immediately whenever a domain's warm-up placement drops.

Which lists matter

For Google Workspace and Microsoft 365 mailboxes, the sending IPs belong to Google or Microsoft and are rarely listed; the domain lists (Spamhaus DBL, SURBL) are what to watch. For IMAP/SMTP mailboxes, the sending IP matters too.

Steps: check a domain

1. Open a multi-list checker such as MXToolbox Blacklist Check or BlacklistMaster.
2. Enter the sending domain (acmehq.com) and run the check.
3. Enter the custom tracking domain (link.acmehq.com) and any domain linked in the email body, and check those too. URL blocklists look at links, not just the From domain.
4. For IMAP/SMTP mailboxes, send a test to your own Gmail, open Show original, find the sending IP in the last Received: header, and check that IP.
5. Record results. A clean check on all major lists means the domain is not the problem; look at warm-up, content and list quality instead.

Steps: delist

1. Open the listing's detail link on the checker. Each list has its own removal page.
2. Fix the cause first. Lists re-add you within days if the behaviour continues. Typical causes: a purchased list with spam traps, bounce rate above 5%, a compromised mailbox, or a link to a listed site.
3. Submit the removal request. Spamhaus, Barracuda and SpamCop remove within 24–48 hours if the form is completed honestly; some lists expire automatically after 7–30 days of no new reports.
4. Pause the domain's mailboxes in OutreachFox while you wait: open the campaign → Sender Accounts and untick them, or set their campaign emails per day to 0 in bulk actions. Keep warm-up running.
5. Re-check after 48 hours. Once clean, resume at half volume for a week.

Steps: ongoing monitoring

1. Set a weekly reminder to run the check on every sending and tracking domain.
2. Watch the Warm up tab's inbox placement for each mailbox; a sudden domain-wide drop is often a listing.
3. Watch campaign bounce rate. A spike in "blocked" or "rejected" bounces with reasons mentioning Spamhaus or "listed" confirms it.
4. When buying through Icemail, rely on its pre-order check, which rejects domains already on BlacklistMaster or SURBL.

Tips

• Never link to a domain you have not checked. A partner's or a customer's blacklisted site in your email is enough to get you filtered.
• Sending domains are cheap. If a domain has been listed on Spamhaus DBL twice, retire it and buy a new one.
• Keep bounce pause at 3%; most listings start from bounces that hit spam traps.
• UCEPROTECT and a few small lists cannot be delisted without payment. Do not pay; providers largely ignore them.

Troubleshooting

• Listed but no bounces or placement drop. Minor list; monitor, do not act.
• Delisted but placement still low. Provider-internal reputation lags a week or more. Continue reduced volume with warm-up.
• IP listed for a Google/Microsoft mailbox. Almost always a shared range false positive; nothing to do.

Related articles

• Landing in spam? The recovery playbook
• Deliverability fundamentals for cold email
• Troubleshooting warmup (paused, low health score, high spam placement)
• Enable bounce protection (pause at X% bounce)
• Set up a custom tracking domain
• How Icemail automates SPF, DKIM and DMARC — and replaces mailboxes for free