Sending email only to active (unblocked) users of the site How can I send email and notifications to the active (unlocked) users of the site? What modules do I need for that? Could you explain it clearly?  

Already I'm using messaging, notifications and the Mass contact module. 
If I send mail through the Mass contact module, the blocked users also receive mails.
Add a category in Mass Contact

http://localhost/sitename/admin/config/system/mass_contact/add

and "Roles to receive e-mail" , just check "authenticated user" and save configuration.

And "authenticated user" are active user not the blocked user.