Best Email Blacklist Prevention Practices 2023

The Warmup Inbox Team
The Warmup Inbox Team

(Note: Some have started using the term “blocklist” in place of “blacklist” because of negative associations with the word. Both words have the same meaning and can be used interchangeably.)

What Is A Blacklist?

An email blacklist is an online database that collects email addresses and domains that have been reported as sending out spam or malicious content. ISPs use blocklists as a reference to determine how safe it is to accept messages coming from unknown domains and addresses.

Blocklists can cause many problems for your marketing campaigns because the time and effort you spend creating content will be wasted. Being placed on a blocklist is like having an immediate ban placed on your content, regardless of whether you’ve been sending out malicious content or not.

How Do Email Blacklists Work?

Every email address is attached to a specific IP address that allows ISPs to know where a message originates. IP addresses are like return addresses on letters or packages sent through snail mail. IP addresses allow ISPs to trace the location of the sender.

When an ISP gets a message, they first check the sender’s IP address across the DNS blocklists. If the IP address matches one on a blocklist, the ISP rejects the email. If the IP address doesn’t have a match, the ISP will run a couple more security checks before permitting the message to go through. While these lists aren’t the only thing that affects deliverability, they can have a severe and sudden impact if you end up on one.

Different Types of Email Blacklists

There are four main types of email blacklists that affect email deliverability:

New Domain Email Blacklists

This category includes blocklists such as Sem Fresh, where a newly registered domain under a domain provider is automatically added to a blacklist for one to two weeks after its creation. These lists are intended to prevent spammers from mass creating new domains to send out mass emails.

Spam Trap Email Blacklists

ESP providers will take email addresses that have been abandoned for a specific time and set them up as a spam trap to detect when people send out a lot of spam mail. If anyone attempts to reach out to this long-dormant email address, they’re automatically added to a specific blocklist. Realistically, if the email address has been abandoned with no activity or interaction in years, attempting contact with it looks suspicious. These lists are relatively easy to stay off of, as long as you constantly update your database and don’t buy old email lists.

Phishing/Ransomware Blacklists

If any domain or IP is caught sending any type of email intended to harvest or steal personal information of any kind from the recipient, they will be added to a specific blocklist. This is the most challenging list to get a domain or IP address removed from because these lists identify the most destructive types of email users.

Spam Blacklist

And the one marketing teams are likely to end up on if they send enough emails: the spam blocklist. These are the most common lists because they’re generalized, but they’re also the easiest lists to repair.

Reasons Why Your Email Has Been Blacklisted

Blocklists were created to protect consumers from unwanted emails. If you aren’t a spammer, you shouldn’t have too much trouble getting yourself off a blocklist. There are multiple ways to get placed on a blocklist, including:

  • A Hacked Account – When a professional email ends up on a blocklist, it’s generally because a cybercriminal hacks their account and sends out malicious emails under their IP address. Many people don’t notice that their account has been hacked until they run out of storage or a recipient tells them about a strange message they received from “them.”
  • A Dirty Mail List – Consistently sending out emails to inactive or fake email addresses can decrease your engagement rates and land your IP address on a blocklist. Additionally, if you buy an email list from someone, there’s a high probability that the list is filled with old emails and spam traps.
  • Multiple Messages Flagged as Spam – Whether your recipients are consciously marking your content as spam or their ISPs are sorting you into the junk folder, numerous spam complaints can damage your reputation to the point that you’re added to a blocklist.
  • Suddenly High Volume of Emails – If you don’t warm up your IP address, ISPs may think you’re a spammer and place you on a blocklist if you suddenly begin sending out bulk emails.

Ways to Check if Your Email Has Been Blacklisted

There are multiple online tools you can use to check if your IP address or domain is on a blocklist:

  • Barracuda Reputation Block List: free DNS blacklist that lists emails known to send spam
  • Invaluement: anti-spam DNSBL that blocks senders who send out unsolicited mass emails
  • MXToolBox:a way to check multiple blacklists quickly and check your DNS
  • MultiRBL:free multiple DNS service that cross-references lists by IPV4, IPV6, or domain
  • SpamCop:a list of IPs that have been reported as spam by SpamCop users
  • SpamHaus:DNSBLs used to identify and track spam sources
  • SURBL:lists of websites that have appeared in unsolicited messages
  • Warmup Inbox: as a part of our platform, we constantly run checks to make sure you’re not on any blocklists

Why Does Blacklisting Cause my Email to Bounce Back to Me?

When your IP address or domain is blacklisted, ISPs won’t allow your message to reach the recipient. If you were to send a letter with a return address via snail mail, but you write the recipient’s address wrong, the letter will make its way back to you. In the same way, when you’re placed on a blocklist, the ISP will send the message back to you to let you know that the email couldn’t be delivered.

If you know the intended recipient and can communicate with them outside of email, you can always ask them to add your address to their list of approved senders. Or you can figure out which blocklist you’re on and work to get your address taken off of it and start warming your IP again.

How to Avoid Getting Your Email Account Blacklisted

Instead of waiting to remedy the situation when you’re placed on a blocklist, you can take defensive measures to avoid having to go through the hassle of getting your name removed. This also spares you from missing out on time that you could use to engage with your customers.

  • Update Your Email List Frequently – If an email bounces, remove it from your list or find a way to correct the email address if it’s typed in wrong. Multiple bounced emails indicate that you’re randomly sending out emails and can damage your reputation. Additionally, don’t buy email lists to generate leads. These lists are often filled with fake emails or spam traps, and in the long run, it’s better to put in the work to gain leads organically.
  • Provide an Unsubscribe Link -- If you give customers the chance to unsubscribe from your emails, they can request to stop receiving emails from you instead of flagging your content as spam. Just be sure to honor their request as soon as you can.
  • Use a Double Opt-In Method – Have your customers verify that they want to receive your emails and give them the chance to confirm that their email is correct before you start sending them messages.
  • Warm Up Your IP – When setting up a new IP or working to improve the tarnished reputation of an older IP, ramp up the number of emails you send within a day and week. This allows ISPs to recognize you as a trustworthy sender and will get your messages sent right to your recipient’s inbox. Try Warmup Inbox for free to see how you can seamlessly and effortlessly warm up your IP.