Other non-primary email addresses can be used in case the primary address gets bounced. Edit the profile and mark any other address as primary.
Marking an email address as Primary
Only one email address can be marked as primary.
Every record must have a primary email address.
Note: The only exception is when you don't have an email address for a record.
If there is only one email address in a profile then that is marked as primary by default.
Reach out to us at firstname.lastname@example.org in case of any queries.