Google has finally integrated Google Drive into their Gmail platform. You can now share files from Drive into mails without leaving Gmail.

Gmail would check if the recipient of the email have the required permissions to access the files. Google does even better. It would check for the permissions if you insert a Google Drive file link manually into the mail body.

Google said:

Like a smart assistant, Gmail will also double-check that your recipients all have access to any files you’re sending. This works like Gmail’s forgotten attachment detector: whenever you send a file from Drive that isn’t shared with everyone, you’ll be prompted with the option to change the file’s sharing settings without leaving your email. It’ll even work with Drive links pasted directly into emails.