All conversation via email.
There are cases, when email thread becomes a legally binding agreement.
One recent New York decision found that given the now widespread use of email as a form of written communication in both personal and business affairs, it would be unreasonable to conclude that email messages are incapable of conforming to the criteria of (the New York version of the UETA) simply because they cannot be physically signed in a traditional fashion
You can check this link for the full text and more examples:
https://www.legal.io/guide/551c797e777777655d8e0000/What-Do-You-Mean-We-Have-A-Contract-How-to-Prevent-an-Email-Exchange-From-Inadvertently-Becoming-a-Binding-ContractHowever, any dedicated electronic or paper contract will be better for the enforcement, since it will have a better structure and clearer terms, rather than an email thread, which will be a subject to interpretation.