Sent immediately after self-serve signup. Confirms the account, names one next step, opens a reply channel.
One next action and one time estimate. Tells the user what to do without listing every feature. Reply invitation works because founders actually answer in the early days.
Single CTA. A specific time estimate ("takes 90 seconds"). A from-the-founder line for the first 1,000 signups.
A welcome that lists every feature. Multiple CTAs. A generic "thanks for signing up" with no instruction.