A blacklisted domain is a website address (URL) that has been flagged by security services or organizations for potentially malicious activity.

These blacklists help protect users from threats like spam, phishing attacks, malware distribution, and other harmful content. When a domain is blacklisted, it essentially gets a bad reputation online.

There are several reasons why a domain might end up on a blacklist:

1. Spam: Sending unsolicited bulk emails (spam) is a major cause of blacklisting. If a domain is associated with sending a high volume of spam, it can be flagged.
2. Phishing: Websites designed to steal personal information by mimicking legitimate sites can be blacklisted.
3. Malware: Domains that host or distribute malware (malicious software) will likely be blacklisted.
4. Other Malicious Activity: Activities like hosting illegal content, copyright infringement, or denial-of-service attacks can also lead to blacklisting.
5. Improper Email Configuration: In some cases, even legitimate domains can be blacklisted due to poorly configured email servers that accidentally send out spam.

Domain/IP Blacklist Checker Tool is an online utility designed to help users determine whether their IP or domain has been flagged and listed on various blacklists.

These blacklists are maintained by security services and organisations to identify websites and IPs associated with malicious activities.

• www is the subdomain and is an identifier of the record.

• CNAME is the DNS record type.

• com is the value of the record. That means www will resolve to the IP address of the domain abc.com.

• 3600 is TTL (time to live) is the expiry time of the CNAME record. It's expressed in seconds. Here 3600 means that the records will be updated after each hour.