Definition
A blocklist (also called a blacklist) is a database of IP addresses, domains or senders that have been flagged for sending spam or poor-quality mail. Email providers and filtering services consult these lists and may block or filter mail coming from a listed source.
A blocklist placement is serious because it can stop your mail being delivered to many recipients at once. It usually follows spam complaints, high bounces or habitual bad sending. Recovery requires identifying why you were listed, fixing the cause, and requesting removal — a process that takes time and a clean record.
What Blocklists Track
| Listing | What Is Flagged |
|---|---|
| IP address | A specific sending server |
| Domain | The sending or branding domain |
| Sender | A particular sender identity |
Any of these can be listed.
Why Senders Get Blocklisted
| Cause | How It Happens |
|---|---|
| Spam complaints | Too many recipients report mail |
| Trap hits | Sending to spam-trap addresses |
| High bounces | Poor list hygiene |
| Bad sending | Habitual poor mail behaviour |
Improper sending triggers placement.
How to Recover From a Blocklist
- Identify the listing: Determine which list and entry.
- Find the cause: Understand why you were placed.
- Fix the issue: Correct the sending practice or list.
- Request removal: Apply for delisting after the fix.
- Rebuild reputation: Send cleanly to recover standing.
Related Glossary Terms
Abuse Complaint
An abuse complaint is a report from a recipient who marks an email as spam, which negatively affects sender reputation and deliverability.
Alt Text
Alt text is the written alternative to an image in an email, displayed when images are blocked, slow to load, or consumed by screen readers.
AOL Mail for Email Marketers
AOL Mail is a legacy email provider with specific deliverability requirements and rendering quirks, now operating as part of the Yahoo+AOL network under shared infrastructure.
Email Authentication Protocols
Email authentication protocols are technical standards that verify the identity of an email sender, helping mailbox providers distinguish legitimate mail from spam and phishing.
BIMI
BIMI (Brand Indicators for Message Identification) is an email standard that allows brands to display their logo next to their emails in supported email clients. It requires DMARC enforcement at quarantine or reject policy.
Bounce Management
Bounce management is the process of handling emails that are rejected by mailbox providers, including classification, removal of bad addresses and protection of sender reputation.
Frequently Asked Questions
A blocklist is a database of IPs, domains or senders flagged for spam or poor-quality mail. Providers and filters consult it and may block or filter mail from a listed source.
Placement typically follows triggers such as a high volume of spam complaints, hitting spam-trap addresses, high bounce rates, or other bad sending behaviour. These signals cause filters to flag your source as risky.
Use blocklist monitoring or look up services to check whether your IP or domain appears. Many monitoring tools report blocklist status alongside your deliverability metrics, so you can see a placement before it affects delivery.
It depends on the list and how clean your sending is afterward. You must identify and fix the cause, request removal, and then send cleanly to rebuild reputation. The process can range from days to longer, depending on the situation and list.