By "Social Proof" I mean some validation that the sender is a genuine human. Not spam, drip-campaign, mass marketing, etc.

Examples in social media:

- Twitter: When reaching out via twitter, you have followers. Which embeds a certain amount of social trust. i.e. "if other people like this person, they can't be that bad"

- LinkedIn: Similar to twitter. But less validation, since you can just request connections to reach that 500+ number.

- Discord/Slack: Invite system. At some point someone in the community invited the member. So there has been some level of validation.

- Keybase: Requires setting up a Public/Private key pair. Demonstrates basic level of competency.

Question inspired by spending the last 6 months doing email marketing. It's not great. But it's the one direct line of communication that everyone has.