[krageon]

Is this situation not the same as verbally binding legal contracts? What you need is to record your expiring messages otherwise it'll just devolve into a they said, they said in the courtroom.

[prima-facie]

It's not the same. In business Email is established as a written form of agreement.

[krageon]

This isn't email, so I don't see how that is applicable.

[fouc]

Applies to any written form of communication

[sib]

In the US, at least, there is a significantly differently model of validity of written and oral agreements.