Email Record in CRM Question

Does the Email only get recorded from 1 email address on a Contact?

For instance, the Contact, I have added the custom field Alternative Email for a field of email address that could be their personal address. It's in their record.

However, emails from or to that address are not being recorded into CRM.

Do I need to set up the custom email field differently to record properly, or does it only accept one email address?

Thanks.