An email blacklist is a list of IP addresses or domain names that have been connected to spam or other unwanted email.
Email providers and spam filters can use these lists to help decide whether a message should be delivered to someone's inbox, placed in the spam folder, or rejected.
You may also hear an email blacklist called a blocklist, DNS blacklist (DNSBL), or real-time blacklist (RBL).
How Does an Email Blacklist Work?
When an email server receives a message, it can perform several checks before accepting it.
One of those checks may be to see whether the IP address of the server sending the email appears on a blacklist.
For example:
- Your mail server sends an email.
- The receiving mail server checks the sending IP address.
- It may check one or more email blacklists.
- If the IP is listed, the receiving server decides what to do with the message.
A blacklist usually does not make the final decision. The receiving email provider decides how much importance to give a particular blacklist.
Why Does an IP Address Get Blacklisted?
An IP address can be listed for many reasons. Some common causes include:
- Sending large amounts of spam
- A hacked email account sending unwanted messages
- A compromised website sending spam
- Malware running on a server
- Poorly configured email software
- Sending email to addresses that do not exist
- Receiving a large number of spam complaints
- Sending to email addresses that never asked to receive messages
Sometimes an IP address may also have a poor reputation because of activity that happened before the current user received the IP.
Does Being on a Blacklist Mean My Email Will Not Work?
Not necessarily.
There are many different email blacklists, and email providers do not all use the same ones.
An IP address could appear on one blacklist while email continues to work normally. Another blacklist may be widely used and have a much larger effect on email delivery.
Large email providers may also use their own reputation systems instead of relying only on public blacklists.
Because of this, finding your IP address on a blacklist does not automatically mean that your email will be rejected.
Why Is My Email Going to Spam If My IP Is Not Blacklisted?
Blacklists are only one part of email filtering.
Email providers can look at many other things, including:
- The reputation of the sending IP address
- The reputation of the domain
- SPF records
- DKIM signatures
- DMARC policies
- The contents of the message
- Links contained in the message
- How much email is being sent
- How recipients interact with previous messages
- Spam complaints
- Whether messages are being sent to invalid addresses
This means an email can go to the spam folder even when the sending IP address does not appear on any public blacklist.
What Are SPF, DKIM, and DMARC?
These are DNS-based technologies that help email providers determine whether a message is legitimate.
SPF tells receiving servers which mail servers are allowed to send email for your domain.
DKIM adds a digital signature to outgoing messages. The receiving server can check that signature to help verify that the message really came from your domain and was not changed along the way.
DMARC works with SPF and DKIM and tells receiving servers how to handle messages that fail authentication checks.
Properly configuring these records can help improve email reliability and protect your domain from being used for fake or unauthorized email.
Can a Website Cause an Email Blacklisting?
Yes.
A website can sometimes be responsible even if you do not normally use it to send email.
For example, an outdated or compromised WordPress website could be used by an attacker to send thousands of spam messages. Contact forms can also be abused if they are not properly protected.
Keeping websites, plugins, themes, and other software updated can help prevent this type of abuse.
Can a Hacked Email Account Cause a Blacklisting?
Yes.
If someone obtains the password to an email account, they may use it to send spam. A large amount of unwanted email sent in a short period of time can damage the reputation of the mail server or lead to a blacklist listing.
Using strong passwords and changing a password immediately when an account may have been compromised can help prevent additional abuse.
How Do I Know If My IP Is Blacklisted?
There are online blacklist-checking services that can check an IP address against multiple public email blacklists.
Keep in mind that appearing on a blacklist does not always mean there is a problem. Some lists are rarely used, while others can have a greater effect on email delivery.
The most useful information often comes from the email rejection message itself.
If an email is rejected because of a blacklist, the error message may identify the blacklist or explain why the receiving server refused the message.
How Do I Get Removed From an Email Blacklist?
Each blacklist has its own removal process.
Before requesting removal, you should first find and correct whatever caused the listing. Otherwise, the IP address may simply be listed again.
Depending on the cause, this could include:
- Securing a compromised email account
- Removing malware from a website
- Updating outdated website software
- Stopping an incorrectly configured mailing script
- Removing invalid addresses from a mailing list
- Correcting mail server or DNS settings
Once the problem has been fixed, you can follow the removal instructions provided by the organization that operates the blacklist.
Some blacklists automatically remove an IP after a period of time if they no longer detect unwanted email.
Can DataPacket Remove My IP From a Blacklist?
DataPacket does not control third-party email blacklists, so we cannot directly remove an IP address from a list operated by another organization.
If you are having an email delivery problem with a DataPacket service, you can contact our support team. Providing the complete email rejection or bounce message is especially helpful because it can show why the receiving mail server rejected the message.
How Can I Help Prevent Email Blacklisting?
Good email practices can greatly reduce the chance of problems.
Keep your websites and applications updated, use strong email passwords, configure SPF, DKIM, and DMARC correctly, and only send bulk or marketing email to people who have agreed to receive it.
You should also pay attention to unusual increases in outgoing email. A sudden increase can be a sign that an email account, website, or application has been compromised.
Most importantly, remember that an email blacklist is only one part of email reputation. Good email delivery depends on the reputation of your server and domain, proper email authentication, the messages you send, and how recipients respond to them.
