New user registration activation email not working

[Stephen]

@tkdhanasekar

smtp_address = "smtp.gmail.com"
smtp_port = 587
smtp_domain = sampledomain.in
smtp_user_name = "mymail@gmail.com"
smtp_password = "*********"
smtp_authentication = login
notification_email = noreply@sampledomain.in
smtp_enable_start_tls = true

Gmail isn’t a supported mail provider. There are lots of reasons that the email can be stopped at Google, my recommendation would be to use one of the supported providers.