When you email, download, or send documents to Dropbox, you have the option to send the files in ZIP format. "Zipped" files are compressed to make the files smaller. They have the following advantages:

• Some email servers are unable to accept large file sizes. Smaller, compressed files are more likely to be received.
• Compressed files take up less space in the recipient's mailbox.
• When downloading, compressed files take up less space on your computer's local drive.