If you are a regular twitter user you will know that twitter sends you email notifications every time there is a new follower or a direct message.
But the twitter service is not the best as you cant follow back people from email itself. Topify is a better way to receive notifications and manage your new followers all via mail.

Topify sends you mails when there is a new follower, the mail consistes of additional information of the person enabling you to decide if you want to follow the person or not. If you want to follow the person all you have to do is hit the reply button and send an empty mail and topify will follow the person for you !

The additional information includes the number of tweets the person has posted , the number of followers he has, number of people he is following and the time when he joined tiwtter along with his bio .

Topify has a similar feature for DM too where you can reply to DM via email and saving from the task of opening an additional tab to log in to twitter to reply

Topify is an invitation only site you can request for invite here Topify | Power Twitter Email Notifications