Quick summary
- What it is: A blacklist (also called blocklist) in the context of email is a public or private database that collects IP addresses and domains identified as.
- What it's for: it helps configure, send, receive and protect email for a domain.
- When to check it: when creating email accounts, configuring an email client or investigating sending and receiving issues.
A blacklist (also called blocklist) in the context of email is a public or private database that collects IP addresses and domains identified as sources of spam, malware or malicious activity. Mail servers consult these lists to decide whether to accept, reject or mark as spam the messages they receive.
Why does an IP or domain end up on a blacklist?
The most common reasons are:
- Sending bulk unsolicited emails (spam).
- A website compromised by malware that automatically sends emails.
- Many bounces from emails sent to non-existent addresses.
- Spam complaints from recipients.
- Being on the same shared server as another account that sends spam (in shared hosting).
How does it affect your emails?
If your server's IP or your domain are on a blacklist, emails you send may:
- Be rejected directly by the recipient server (error 550).
- Arrive in the spam folder instead of the inbox.
- Be held by spam filters without reaching the recipient.
Most well-known blacklists
There are dozens of blacklists. The most consulted by mail servers are: Spamhaus (SBL, XBL, PBL), Barracuda, SORBS and SpamCop.
How to check if you are on a blacklist?
You can check with free tools such as MXToolbox (mxtoolbox.com/blacklists.aspx) or mail-tester.com. Enter your server's IP or your domain and you will see which lists you appear on.
How to get off a blacklist?
The process depends on each list, but generally involves:
- Resolving the problem that caused the listing (cleaning malware, correcting email configuration).
- Requesting removal (delisting) directly on the blacklist's website.
- Waiting between a few hours and several days for mail servers worldwide to update the information.
At Bacan we actively manage the reputation of our IPs. If you have delivery problems, write to us at help@Bacan.
Why it matters in hosting
Understanding this concept will help you make better decisions when managing your service. In practice, it relates to configuring, delivering, receiving and protecting email for a domain. If it appears in a guide, the control panel or a support response, review the context before making changes.
Related articles
- Webmail
- IMAP
- POP3
- SMTP
- SPF