When attempting to save the Form Designer on the Experience platform the following message appears.
WARNING
Your form does not contain a required email field with a remote id of “email”.
When we receive entries without an email address, we store them as anonymous
entries and may not be able to enforce any entry constraints configured (e.g.
one entry per user).
You can ensure all entries are processed with an email address by making sure
your email field is set to “required” and that it has a remote id of “email”.
If you have an email field on the form with the wrong remote id (e.g. “email_01”),
remove it and add a new one to reset the remote id to “email”.
There are a number of use-cases where you might want to allow anonymous entries,
e.g. for a simple audience poll. In these cases, you can choose whether or not
to store the individual, anonymous responses. After you save your form, go to
the Entries area and review the “Data Collection” setting.
Background
This is caused by removing the original Email module and replacing with a new one without saving and closing the form first. The new module gets a Remote Field Name that we don't recognize as the correct email capture field.
Solution
Simply remove the existing email field and replace with a new one. This will revert back to the remote field name by default.