Our email validation engine allows you to use up to six different verification levels. With Syntax's being the lowest level and CatchAll's being the highest one, each level adds additional features and checks to the previous one, building a sort of pyramid of increasing functionalities.
As the level increases, so generally does the time needed to perform the email validation; Syntax validation is typically instantaneous, while MailBox and CatchAll verifications may take some seconds to complete, depending on multiple network factors.
The following table summarizes the different features each verification level offers and includes considerations for the timing of the whole validation process:
|Syntax||Performs a deep syntactical validation of the provided e-mail address against the current IETF standards ( RFC 1123, RFC 2821, RFC 2822, RFC 3490, RFC 3696, RFC 4291, RFC 5321, RFC 5322 and RFC 5336 ).||Syntactical validation is typically instantaneous because it doesn't need to access the external network.|
|Disposable / free||All of the features above, plus: verifies that the provided email address is not a disposable e-mail address (DEA).||Disposable e-mail address check is typically instantaneous.|
|DNS record check||All of the features above, plus: queries the DNS server for information and availability of the email address domain (including DNS MX records).||This verification level requires access to the DNS in order to query information about a given email address domain; DNS queries typically require a very small amount of time (less than one second).|
|SMTP availability||All of the features above, plus: checks if a connection could be performed to the mail server of the e-mail address domain.||This level tries to perform connections to external SMTP servers; the timing for this kind of verification depends on the external contacted servers and on network and infrastructure factors. SMTP verification may last several seconds.|
|Mailbox existence||All of the features above, plus: checks whether the mail server accepts or rejects messages sent to the required e-mail address.||Mailbox verification establishes SMTP dialogs with external SMTP servers, and its timing varies based on external servers' performance, network latency, etc. It may span from some seconds to half a minute or even more.|
|Catch-all||All of the above, plus: checks if the mail server accepts messages sent to the required e-mail address while rejecting messages sent to non existent e-mail addresses.||This level requires more time than the previous one, typically on the order of the time needed by the mailbox verification level.|