Brown's Google Apps service allows each of us to have 30 GB shared storage for email and Google Drive. If you're getting close to your limit or just feel like keeping things clean, you can find big files in your mail and drive using the following instructions.
There's now an easier way to search your emails by size. Open the Advanced Search by clicking the triangle on the inner right of the search box at the top of your email.
You'll see an option to enter a size in the Advanced Search. You might want to start with 15 MB - if you don't find enough results, decrease the number and try again.
Once you delete emails, they will be automatically removed from your trash after 30 days. You can also empty your trash manually.
You can also sort your Google Drive by size to find the biggest files. Find a column heading (such as 'Owner' or 'Last Modified') and click the small triangle next to it. Choose to sort by Quota Used. In Drive, the trash does not automatically empty - if you move a file to the trash and want to lower your used quota, you will have to click the Trash link on the left menu and then the Empty Trash button.