The user fills out the registration form (username, email, password, first and surename, etc.)

Liferay creates the account but does not yet mark it active
Liferay sends a verification e-mail to the user e-mail account with a verification link that activates the account
The user clicks on the link provided and Liferay finally activates the account

Simply by editing portal-ext.properties by adding the following line:

company.security.strangers.verify=true
portal-ext.properties
portal-ext.properties