One of the most frustrating experiences of the electronic age is sending an email, waiting for a reply and later discovering they never got the email. Such mishaps can cost you business, in other words, money. Likewise, it can cost you money when you use email for notification. You send it, call and confirm they got it, discuss the content of the message; and now they claim it never happened or they claim the message was different from what you claim. Electronic communication is easily altered by those technically inclined. You can use paper to avoid the issue, but it is much slower and more cumbersome.
I suggest a good alternative for emails with monetary implications is registered email. A company called RPost has a system to verify an email was received, the time it was received and the content of the message. Just as with regular mail and registered mail with the USPS, it is not something to use on every email, but for truly important emails it provides legalproof of delivery and content. It doesn't take much imagination to see where this system can be of significant benefit to those of us in the real estate industry.