Alan needs to use a service like Constant Contact or Mailchimp for his business emails, but he's concerned that people may not read them or that they won't even get through because of spam and malware. Leo says that's the entire idea behind using those services since they know how to format the email with opt-out options, proper settings, etc.that prevent them from being relegated to Spam filters.
Leo recommends using ShareFile to securely share files. The advantage to this is that the clients won't have to sign up for anything, unlike Google Drive or Dropbox. He can get notified when the client downloads the file, he can set the link to expire, and more. It also has the proper encryption to make it HIPPA compliant.
(Disclaimer: ShareFile is a sponsor).