I have an IMAP server and use SMTP2GO for outbound emails, and I have SMTP2GO working with WordPress via plug-in. But, I need to find the easiest way to respond to an inbound email and also have Double Opt-In.
It seems I need to:
1) pull name and email from the email
2) do a uniqueness check against the WP database for that email
3) add unique users to WP
4) generate an outbound email including users login credentials
Is this a custom programming effort? Or are there plug-ins which can help? Or, WordPress features that can help?