1. Check the server to make sure the email is being sent out.
  2. If the email is being sent out, it could be rejected based on the SPAMMINESS of it. Go to mail-tester.com and test how spammy the email is.
  3. Is it a Gmail account that isn’t receiving the email? It could be some Workspace settings that need to be changed.
    Log in to your google workspace admin account,
    Go to apps/google Workspace / settings for Gmail / Spam, phishing, and malware.
    You can enter the IP of your server on the “Email allowlist” to always accept emails from your server.