3 Email Validation Terms You Should Know

email-validationEmail validation is an important tool in ensuring the deliverability of your email messages. Not only can email validation correct common typos and weed out bogus email addresses, it is also essential in protecting your reputation with many large mail providers. After all, if a mail provider or mail server thinks you’re a spammer, NONE of your messages will go through because you’ve been “blacklisted.” What does this mean? How can you avoid it? With these questions in mind, let’s go over three email validation terms and what they mean to senders of mass email.


Mail servers maintain several lists, from white to black, in an attempt to keep spam from entering the inboxes of their customers. They don’t take any chances; if it looks like you’re sending spam (such as by sending too many messages to non-existent email addresses or using “scraped” email addresses), you’ll be treated like a spammer. On the other hand, if you play by the rules, you’ll earn their trust. Mail servers can group domains, IP address, and email addresses into three types of lists: white, gray/silver, and black.

  • Whitelist — Ideally, you want to be on the whitelist. A whitelist is often referred to as an “allow” list. Whitelists can contain domains, IP addresses, or email addresses. Because these are trusted senders, messages sent by whitelist members generally bypass some or all of the mail server’s security measures. Their messages are allowed to go through.
  • Graylist — Also referred to as a silver list, graylists sit between whitelists and blacklists. Graylists are typically used to temporarily block and reject email messages from new and unknown IP addresses, a process known as a “soft bounce.” This is a defense mechanism employed by mail servers to protect themselves from spam when encountering an IP address or domain for the first time. It is not uncommon to receive a soft bounce when sending a message to a new domain for the first time. Soft bounces typically resolve themselves. For example, if the recipient’s email address is valid and you try sending the message again, the message will be accepted and delivered.
  • Blacklist — Blacklists are also known as “blocklists” because they permanently block any and all messages from members on the list. Blacklists consists of domains, IP addresses, or email addresses. If your domain, IP address, or email address in on a blacklist, your messages will be permanently blocked and rejected, a process known as a “hard bounce.” Unlike soft bounces which tend to resolve themselves, a hard bounce is permanent unless the IP address, domain, or email address is removed from the blacklist. Similarly, if you attempt to send email to a blacklisted domain or IP, there is a chance that the message will bounce back.

Mail providers aren’t the only ones to use whitelists and blacklists. For example, interoffice email from your company’s own domain is far more trustworthy than some random @gmail address. Thus, network firewalls and mail servers are often configured to use whitelists and blacklists consisting of domains or IP addresses. End users often use personal blacklists to reject or filter specific email addresses.

DOTS Email Validation helps you to stay off of blacklists by validating and correcting common address mistakes that could lead to hard bounces and subsequent blacklisting. This email validation service also warns you of spam traps, honeypots (stay tuned for a post on this!), and known spammers — each of which could cause you to be blacklisted.