What's a blacklist?

An email blacklist is a list of IP addresses or domains that are suspected of sending spam via email.

Various blacklists are maintained by different blacklist providers across the internet, and are used by email services to prevent unwanted spam from ever reaching the intended recipients.  Different mailbox providers may use different combinations of blacklists along with their own internal metrics to decide whether or not to deliver an email to the intended inbox based on where it came from.

Not all blacklists are created equal

There are a lot of blacklists out there (over 300 as of last count) that are maintained by different sources.  Some of them follow good business practices, maintain reliable lists, and provide reasonable options for reputable senders to get removed from the blacklist in the event they are mistakenly flagged as spammers.  

Others are less reliable, may be overzealous in blacklisting entire swaths of IP ranges based on any suspicion of spam coming from a similar IP, or may have no way to request removal from their blacklist.  Believe it or not, some blacklists are active scammers themselves, in that they will blacklist reputable senders and then require monetary payment to be removed from their list.

Generally speaking, there are some highly trusted blacklists which are used extensively across the web, and there are some widely distrusted blacklists which are hardly ever used, or are used very minimally across the web.

Fuse's Spam Analysis tool says I'm on a blacklist. Should I be worried?

Fuse's Spam Analysis tool checks to see if you may experience any delivery problems with an email due to appearing on one or more blacklists.

Based on the descriptions above, you may have already surmised that discovering yourself on a blacklist may or may not actually be a problem.

Here are 3 important things to consider when you find yourself on a blacklist:

  1. We regularly monitor the emailing reputation of our sending service, and strive to maintain a high rate of deliverability for you and all of our clients.  Our reputation relies on your reputation, so your reputation and your email deliverability rate is of utmost importance to us!
  2. If you find yourself on a blacklist that you aren't familiar with, please check the list below.  If you don't see any information about the list on this page, please reach out to our support team and we'll actively look into it.
  3. There are some blacklists that, quite frankly, are not concerning.  If any of the following blacklists appear in your Spam Analysis, our most helpful advice will be to take a deep breath of relief, and keep on emailing.  Even while listed on these blacklists, Fuse's overall email delivery rate remains consistently above all industry averages by anywhere between 6 to 30 percentage points over other comparable systems.

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SPECIFIC BLACKLIST SUMMARIES:

SORBS

There are a few variations of this list name including SORBS, SORBS-SPAM, SORBS-NEW, etc.

Based on the combined experience of our team plus input from a myriad of email administrators across the web, SORBS is one list that is currently nothing to be concerned about. Here's why:

  • SORBS is known to add ranges of IP addresses to its list based on the behavior of one neighboring IP address.  In oversimplified terms, if 1,000 people were sending email and SORBS suspected sender number 73 of sending spam, they might blacklist all senders between 50-100 because number 73 falls within that range, thereby penalizing several senders for no reason (note: these are not actual statistics, just a generalized description of why the blacklist is unreliable).
  • SORBS also holds IP addresses for ransom.  Once you've been blacklisted, you must pay them to request removal from their blacklist.  However, there is no guarantee that they won't blacklist you again and ask for another payment.

Due to the questionable practices described above, SORBS often ends up blocking valid emails, is therefore distrusted by many email service administrators, and is not widely utilized as a spam blocking source.

Bottom line: if you're blacklisted with SORBS, don't worry about it.  The effect on your deliverability will be minimal if it has any effect at all.

UCEPROTECTL2

Email sending services and email reputation monitors alike, both generally list UCEPROTECTL2 as a "Very Low Importance" blacklist.  It is specifically and exclusively used by a portion of email systems based in Germany, Austria, and Switzerland, so it does not affect US or Canadian email systems.

ZapBL

This one is generally listed as a "low importance" blacklist.

According to their own descriptions, ZapBL does not directly block emails. It is simply a "list of opinions" of some email administrators who use their service as a place to identify IP address that might be spamming.  

In other words, someone who uses the ZapBL list can add any IP to the list and it will remain there as a blacklisted IP.  They will only de-list the IP if the IP administrator pays them for "consulting time".  To translate that, they are a list of IP's that may be suspected of spam based on any list user's opinion, and they basically hold the IP ransom, asking for payment to be de-listed.  This list is not widely used so email sending services and monitors (including mxtoolbox) list it as "low importance".  This list would only cause a delivery failure if the intended recipient has an email system setup that specifically references the ZapBL list, which is rare.

OTHER BLACKLISTS

If the Spam Analysis tool says you are listed on any blacklist other than those listed above, please contact the Fuse support team and let us know.  We will be more than happy to look into it in order to protect your email reputation, and ours!

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