How can I send out emails to my customers from a web browser or when I am away from the office?

You can use Mochahosts convenient WebMail feature. You can access your email as well as send out emails from your domain name through a web browser anywhere you have an Internet connection.

Simply type 

For Linux plans:

https://www.yourdomain.com/webmail/

For Windows plans:

https://webmail.yourdomain.com