How to send emails using workflow based on the email addresses mentioned in the custom email field?

Dear Team,

Hope you are well.

I am looking for an idea on how to achieve this requirement.

I have 2 Email fields in Lead form (One is OOB field and One is custom created email field). I have created a workflow to automatically send registration emails to email addresses specified in both the email fields. But in the workflow I cant seem to select the Custom created email field in either To or CC fields of email, only OOB field is listed.

How do I configure to send email to the email addresses mentioned in Custom created field using workflow?

Thanks

Gowtham