“You can’t fax a handshake” is a business expression that means there is no substitute for face-to-face contact with a client. “You can’t fax a handshake” was a slogan used by travel agents in 1991 and in advertisements for Northwest Airlines later in the 1990s. The expression is still used; in 2009, the New York (NY) Times explained, “The saying is often trotted out on Wall Street when people need to be reminded of the importance of getting on a plane and seeing a client.”
 
 
12 April 1991, St. Petersburg (FL) Times, “Travel agents see upturn for summer” by Kim Norris, pg. 2E:
The coalition (American Society of Travel Agents—ed.) is using the slogans, “You can’t fax a handshake” and “You can’t send a hug through the mail.”
 
Google Books
The Global Leader:
Critical factors for creating the world class organization
By Terence Brake
Chicago, IL: Irwin Professional Pub.
1997
Pg. 15:
But remember, to paraphrase a recent Northwest Airlines advertisement, “You can’t fax a handshake, or the look in someone’s eye.”
 
New York (NY) Times
A Ritual Loses Its Grip
By ADAM BRYANT
Published: July 06, 1997
HANDSHAKES are part of history’s greatest hits: Arafat and Rabin at the White House in 1993; Nixon thrusting out his hand to Zhou Enlai in Beijing in 1972. They are a big reason the airline industry does not feel threatened by the rise of videoconferencing: ‘‘You can’t fax a handshake’’ is a popular saying at many companies.
 
Google Books
Alaska Light:
Ideas and images from a northern land
By Kim Heacox
Santa Barbara, CA: Companion Press
1998
Pg. 112:
You are too many to list, and I fear some would be missed if I attempted, so allow me to find you again in person, because I cannot fax a handshake or e-mail a smile.
   
New York (NY) Times
A NATION CHALLENGED: THE MEETINGS; Remote Rendezvous
By AMY HARMON
Published: September 24, 2001
(...)
No one expects a business culture that is filled with maxims like ‘‘you can’t fax a handshake’’ to replace face-to-face meetings with videocameras and Internet chats. But executives across many industries say newly heightened concerns for safety are adding gravity to other factors that were already weighing against frequent business travel: technical advances, stretched schedules and an expanding universe of far-flung offices that are hard to get to.
 
New York (NY) Times
Executives Rethink Life on the Road
By JANE L. LEVERE and NICK BUNKLEY
Published: August 12, 2006
(...)
As a salesman, Mr. Taylor said, “I’m a firm believer that it pays to get in front of the customer.” Indeed, one maxim of business travel is that “you can’t fax a handshake.”
 
New York (NY) Times 
Putting Obama on Hold, in a Hint of Who’s Boss
By ANDREW ROSS SORKIN
Published: December 14, 2009
(...)
There’s an expression that many bankers already know, and might want to keep in mind if they are summoned to Washington again. The saying is often trotted out on Wall Street when people need to be reminded of the importance of getting on a plane and seeing a client: “You can’t fax a handshake.”
 
Cuckoospell 
Tuesday, 15 December 2009
You can’t fax a handshake
I like this expression, which is taken from a New York Times piece about Obama’s recent meeting with Wall Street bankers.