The verification or validation of email addresses is a fundamental requirement in many applications, ranging from the prevention of phishing and other email-based threats through the validation of data entered into an online form to the purification of marketing or other email lists from invalid addresses to maintain sender reputation and avoid bouncing or other unnecessary email traffic.
What exactly is email validation?
Validation refers to the process of determining if the provided email address exists and is capable of receiving emails, as well as collecting some further information about its nature, as described above. Therefore, it should not be confused with methods that determine if an address is malicious or banned; these are two very distinct things.
There are a few different aspects to email verification.
In this section, we’ll walk you through the logical phases of email address validation, which are all handled by the Email Validation API.
Proofreading for grammar and syntax
When it comes to regular expressions, the syntax validation of emails is an often-cited textbook example. Various techniques, some of which are simpler but may fail on some otherwise legitimate email addresses, as well as more complex approaches, are available for consideration. Indeed, any tool that supports regular expressions may be used to do local syntax checking. Nonetheless, the email verification API has a sophisticated common expression built-in, and it will inform us if the text we are validating can be considered an email, at the very least in terms of its structure.
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Checking the domain name system (DNS)
Remember that the first step taken by the MTA is to determine the name of the suitable MX server to connect to. Because of this, it is recommended that you query the MX server for the domain name in the email, “whoisxmlapi.com,” which may be done manually as stated in the preceding section.
However, it is possible that the domain name does not exist at all, in which case the domain name itself should be considered legitimate. This may be easily determined by performing a DNS lookup: a nonexistent domain will result in the host command returning an NXDOMAIN response. If, on the other hand, we need to validate an email address, the API will, of course, take care of it for us, and the API will return two sorts of information in the results:
- In this case, the DNS check returns true if the domain exists and false otherwise.
- MX records will offer an accurate list of mail servers that are currently in use. The DNS check may return “true” even if this list is empty or has only a single entry. “In this case, it implies that the domain itself exists but is not set for email exchange.
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Check the SMTP server.
Upon determining that the domain exists and that MX servers have been designated, the next step is to determine which of the MX servers can really be linked through SMTP. Precisely, this is accomplished by establishing a conversation with the address being validated and finally simulating a mail sending operation to the address being validated.
Again, this may be accomplished manually, for example, by connecting to the servers through telnet, as explained before, and carrying out the necessary dialogue. However, as previously stated, it may be hard to access a workstation’s IP address due to the firewall restrictions in our network. As a result, there is the possibility that our simulated email sending communication will be flagged as suspicious by some defensive automatism on the mail server’s end, mainly if we send to a large number of addresses at once. As a result, our IP address may be banned, which is a bad outcome.
Fortunately, the API takes care of this for us. If at least one MX server could be successfully connected and was ready to accept emails for the address, the field smtp Check will be set to true in the response. If this is not the case, the value of the field will be false.
