If you find yourself using loads of space in Gmail - one reason can be that you attach documents on every email. The result here is that every document adds space as it is a physical copy of each document. 

A better way to send files is to use the attach via Google Drive option - watch the video below for how to do this. 

The end result is two fold: 

1) You don't send a copy every time and therefore the email is much smaller 

2) You have the option to maintain control over what you have sent, by setting the security settings appropriately for the file. 

If it's a brochure of services for example, you can also use the same link over and over again in a template, without need ing to have the extra clicks to attach the file (so there's a productivity win too)! 

Now you can learn about how to share securely with non Google accounts, mentioned in the video above.