What are the main aspects of e-mail validation?
A wide variety of applications require the validation or authentication of e-mail addresses, from protecting users against online fraud and various types of email-based threats to purging advertising or other e-mail lists of invalid addresses in order to sustain sender reputation and evade bounces and some other unneeded e-mail traffic. Several other blogs have discussed them in further depth.
What is the purpose of e-mail validation?
This means verifying that the supplied e-mail address exists and is capable of receiving e-mails, as well as getting some further information about the address's nature. That's distinct from determining whether or not an address is malicious or banned.
It is the primary goal of this paper to provide an overview of the key components of validation and to demonstrate how this may be accomplished using the email validation. Many e-mail addresses can be validated rapidly, either individually or in bulk, and may even be automated as part of a larger program.
E-mail verification: certain aspects
Check the syntax
Regular expressions are commonly used in textbooks to validate the grammar of e-mails. In addition, there are more complex techniques that may fail with some legitimate e-mail addresses. With regular expressions, any tool that provides syntax validation may be used locally. This API includes a data structure built in that will tell us if the text we are validating is an e-mail at especially in terms of grammar.
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 missing domain will lead to the host command returning an NXDOMAIN response. If, on the other hand, we need to authenticate an e-mail 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 unless the domain exists and false otherwise.
- · MX records will offer the real list of mail servers that are currently in use. It is possible that the DNS check will 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 e-mail exchange.
Check the SMTP protocol.
This step is necessary if the domain is existent and there are MX servers nominated. Initial contact is established, followed by a mail-sending simulation of the e-mail being confirmed.
The same procedure as above may be performed manually, e.g., by connecting to the servers through telnet and having the required discussion. It may, however, be difficult to access a workstation's IP due to firewall regulations in our network. Defensive automatism on the mail server's part may flag our e-mail sending simulation as suspicious, especially if we send to a large number of addresses at once. As a result, our IP address may be banned.
Check the kind of mail provider.
In addition, it may be of interest to determine if the e-mail address corresponds to a free e-mail service provider such as Yahoo! It's possible to find out by looking up the address in multiple databases, and the API will do just that.