A welcome email can be enough for the user to feel accepted and part of the website and a larger community in general. https://www.shopify.com/blog/14326869-how-to-write-an-effective-welcome-email-13-examples-and-3-templates-you-can-steal-today

https://unbounce.com/email-marketing/ab-test-welcome-emails/

https://blog.markgrowth.com/the-anatomy-of-a-welcome-email-b4f5a0eb3fff

How to write a good email:
https://medium.com/freelan-ce-ship/you-must-learn-how-to-write-a-damn-good-email-1c8087e02c40

Example:

Examples of emails from big companies:
https://www.goodemailcopy.com