Sending email from PHP is often automatic and simple if setup on a traditional hosting account – however the mail() function in PHP does not work on AWS EC2 servers. AWS requires that you use the SES service. (Simple Email Service).

There are several tutorials that walk you through getting your account setup

To send email FROM your email domains you will need to setup and authorize the domain (See TIP #1 below)
https://docs.aws.amazon.com/ses/latest/DeveloperGuide/verify-domains.html

The step that is often missed is that outgoing email in new accounts is allowed ONLY to the email addresses you verify – to verify individual emails addresses.
https://docs.aws.amazon.com/ses/latest/DeveloperGuide/verify-email-addresses.html

To enable your account to send email from your verified domains, and to ANY email address, you will need to get the account removed from the sandbox mode (check the Email Sending -> Sending Statistics page for a message) Click the ‘Request a Sending Limit Increase’ button to ask to remove the account from the sandbox. (here is a tutorial –
https://docs.aws.amazon.com/ses/latest/DeveloperGuide/request-production-access.html )

TIP #1: I would suggest using route 53 for DNS for your domains, as it is a simple couple button clicks to authorize the domains, and get DKIM setup

TIP #2: make sure that you have posted a privacy policy or an email policy on your site – which explains how you send emails and handle their email information. Include a link to your policy in your request for removal from the sandbox.