What is macro for getting email id in email template?

The system resolves dynamically macros when sending the emails. If macros in your template are not resolved correctly - it means there is insufficient context to resolve: for ex. {%Email%} portion of your macro and it usually returns empty string, but you are getting 'firstname.lastname@yourdomain.com'...

Anyway, if I am not mistaken for On-line marketing macros you can use

{%OnlineMarketingContext.CurrentContact.ContactEmail|(identity)GlobalAdministrator%}

using {% Email %} should give you something like john@mail.com if you send out the actual email. But if you are only using preview or test email, if you only firstname.lastname@yourdomain.com which is the default because the test email does have any data the macro can resolve from.