Email is the most efficient, cost-effective and speedy method of communicating information. It's an easy and instantaneous alternative to traffic jams, delays in postal delivery, fax machine disruptions, and crowded telephone lines. The ease of email may obscure its inherent risks when it comes to sharing sensitive documents.
Once your personal information is gone from your server there is no way to control where it goes and whom it is visible to. Even if you have email encryption, which adds an additional layer of security, it may not protect against the kind of "man-in-the-middle" attacks that could occur if someone were to intercept your email messages while it was in transit.
It is best to use a third-party that specializes in secure document exchange. This will ensure that the confidential information of your customers will never fall into the improper hands. A secure document exchange system lets you monitor the users and editors of your customer's personal data.
If you must email sensitive information, an NDA that is a good fit can help you manage the risks. For instance, limit the number of specific information items you send only to what is necessary to complete your work and avoid including them in multiple emails. Use a password protected file instead of attaching it to an email. You can also include a confidentiality statement in your emails. No matter which method you choose to use, be sure you clearly state your expectations in your NDAs for recipients of confidential information.