Every address you send for verification (or any email address we find for you) will have a result that is either "verified", "unverified", or "unknown".
Here's what each means:
Verified. A verified result means the recipient's mail server stated the recipient was "OK" to send a message to. Note: If we classify an address as "Accept All", the message still may bounce, even though the result was valid. See "Accept All" for more details.
Invalid. An Invalid result means the email address does not exist, or is syntactically incorrect (and thus does not exist).
Unknown. Prospectifier returns an unknown result when it was unable to get a response from the recipient's mail server. This often happens if the destination mail server is too slow or temporarily unavailable. In some cases, retrying your request after about 5 minutes will return a Verified or Invalid response. Unknown addresses don't count against your credit balance.
Accept All. Some domains accept all email you attempt to send to them. Typically, these domains are trying to protect their legitimate users by telling the sending mail server it will accept the mail for a given email address, but then silently discard the message or send a bounce message after the fact. In these cases, it is impossible for Prospectifier to determine if the email will in fact be delivered to a user's inbox.
Sending to an Accept All domain may increase your bounce rates and/or lower your open rates. Therefore, use a degree of caution when sending to Accept All domains. Unlike other solutions, we do not charge you a credit for an Accept All result.
Disposable Email Address. Email addresses that point to domains like trashmail.com, and mailinator.com, are utilizing a disposable email service. These services enable users to create one-time email addresses in order to receive initial communications from a service (such as an activation email) and then are discarded.
Free Email Address. Prospectifier identifies mail addresses that are using free services such as Gmail and Yahoo! Mail. In many cases, it is perfectly acceptable to send email to a user of a free email service. However, in certain contexts, businesses can receive better open/response rates when only sending to non-free email addresses.
Role Email Address. A role email is an address that's typically associated with a function (postmaster, support, sales, etc.) instead of a person. In some instances, mailing to a role address can lead to a decreased open rate and is generally advised against while sending marketing email.