Question

I would like to only allow email addresses which are valid and non public email addresses eg gmail,yahoo, hotmail etc.

Can anyone help me out check for this? Im guessing i would need to use a regular expression but not sure if there is an easier way

Answer 1

If you only need to filter on the top level domain, then you could use something like this:

^[a-z0-9._%+-]+@[a-z0-9.-]+\.(?:edu|gov|mil)$

This will only validate email address ending with .edu, .gov, or .mil. For instance,

[e-mail] <- valid
[e-mail] <- invalid
[e-mail] <- valid
[e-mail] <- invalid

Note: these will all assume that the regex option of Ignore Case is turned on.

If you’d also like to allow for two-letter top level domain country codes, like .fr or .ca, you could add an expression for that like this:

^[a-z0-9._%+-]+@[a-z0-9.-]+\.(?:[a-z]{2}|edu|gov|mil)$

If instead you want to exclude the “big three” email hosts, you could use something like this:

^[a-z0-9._%+-]+@(?!gmail\.com|yahoo\.com|hotmail\.com)(?:[a-z0-9.-]+\.?)+$

(this uses look-ahead assertion with the (?!) “match if suffix is not present” grouping) Examples:

[e-mail] <- valid
[e-mail] <- invalid
[e-mail] <- valid
[e-mail] <- valid

More regex examples for email address validation can be found here.