Sending e-mail from Confluence with Groovy, ScriptRunner to a user who has signed up

[Ian]

I want to send an email to a user who has signed up as I have activated the signup option.

I have tested the script for the email and the email is being sent now I want to send email to the user who has signed up by setting the below code to the email of the user who has signed up:

Email email = new Email("<signed up user email address>");

How can I get the email of the user who has signed up and place it in the above code using groovy script?