Private microsites with access controlled via @company-domain.com email validation

Hi, first time user!
New user of Web flow, apologies if the solution to this is very easy and I’ve missed it!

Here goes……

The proposition we’re looking to build involves us hosting a number of small microsites, with access controlled via the domain of the email address used to log on. For example, only people with an @company-domain.com is able to access it.

We don’t need any payment processing capability. Any suggestions on how we can best achieve this will be massively appreciated!