Signing design contract electronically?

Okay, everyone says to have a signed contract before doing work. But the problem is that it takes a long time to get a signed contract. First the clients has to "get around to reading and signing" it. And then they have to postal mail it back to me (assuming that they didn't put the wrong address and get lost in the mail).

Also some clients get "cold feet" or intimidated when they read all the legal jargon like ...

- they will be billed extra for work out of scope.
- designer is not liable for anything.
- anything client give designer is within their copyright and authority.
- they have to pay for the postal stamp

etc...

It can take weeks to get a signature. And for a small job that takes hours. Is it really worth it? Is there an easier way to get a signature from them digitally. (Assume that they don't have a scanner).

What I'm asking is if it consider a binding contract if I email them a PDF of the contract, and they email me back saying "sounds good"? And I keep the email as evidence.