To request materials from someone securely:
Go to your MIT Dropbox and choose the dropdown. Choose Request files and complete the form. You can send the link to the person who you are requesting materials from. Let them know that this is a secure link. Download the materials once you receive them and then you can close the link or keep it open if you are waiting on other materials.
To send materials to someone:
* This cannot be done using an MIT business account. If you have a free dropbox or another account you can use it to send files. To send it securely you should use the password protect function.
Go to: https://www.dropbox.com/features/share/file-transfer
Sign into your account. Drop the files in. You can use a password or other features but there may be a charge. Dropbox will generate a link for the recipient.
How Dropbox Keeps your Files Secure (read here)