Ask any programmer the question on how to validate emails and very often the first thing that pops into their minds would be using regular expressions. Regular expression is probably the most common way in any programs to try and match the email address to a specific pattern. The thing is that there are so many combinations of characters that are considered valid for an email address which makes for a monumental task when trying to come up with a regular expression or a series of regular expressions to cover all the cases.
Suffice to say that unless you have studied the RFC standards thoroughly, you would be surprised to find out that the following characters =\/+ are considered valid characters in an email address.
Now consider using MailboxValidator's email validation service. It not only validates the email address syntax but it also does verifications with the mail servers to check if that email address actually exists. For those of you who are doing email marketing campaigns, it also helps that MailboxValidator has checks for role emails which are normally banned by email sending providers.
In short, you get more bang for your buck when you use MailboxValidator versus trying to just check an email address via regular expressions.