[schoen]

In the U.S., many contracts (but not all) can in principle by default be oral and still be enforceable by law.

https://smallbusiness.findlaw.com/business-contracts-forms/w...

[shinigami]

So... no need for DKIM

[tony101]

But you need to be able to prove the existence of the contract. Which DKIM would help with.

[shinigami]

Then digitally sign it. Sign and scan it. Do not require signing every single email you send to protect 0,1% of them.