My previous investors always said that the first 1000 signups to any startup should get a personal email from the founder. I used to send a quick one liner say

My previous investors always said that the first 1000 signups to any startup should get a personal email from the founder. I used to send a quick one liner saying I'm rob, thanks for signing up and let me know if there's anything I can help with. It led to a lot of useful conversations. We already had a running service at the time though, so not 100% sure it transfers to a pure landing page.