A blacklist, in terms of email marketing,is a database created and fed by anti-spam filters, where you can find all those IPs, email addresses, and domains that are considered illegitimate, dangerous, or that have already been reported for spam or irregular activities.
The reasons why your IP address, email address, or domain can be added to a blacklist can be, from the spread of viruses or malicious software to offensive content and mass sending of emails as spam.
How do you know if you’re blacklisted?
To avoid falling into a blacklist, it is best to follow a series of basic recommendations in our email marketing campaigns (see
whitelist), such as clearly identifying yourself as senders or having requested the user’s permission beforehand. But, if you have doubts about whether a company’s emails are being redirected to the spam folder, there are a number of tools to check blacklists.
Among the most used are MXToolbox, DSNQueries or Spamhouse. Its operation is similar: just enter a domain and they tell you if it is on any of the best known blacklists.