How Guest Email Address populates from Contacts
Summary
When you create a Guest from an existing Contact the Guest Email will be populated by the Contact Email.
But if you later update the Contact Email field, the Guest Email address will not be updated, because it’s a separate field of data. While it inherits the Contact Email address on creation, it’s only one way by design.
While this can be confusing, it makes sense because the Contact record is the ‘default’ record of the Contact and the email addresss used might be their main personal email address (for example).
However, when inviting Guests to attend an event in other capacities (perhaps as a guest speaker, supplier or sponsor) you may wish to use a different email address. Guests may request that you use an alternative email address, just for that event (which you can).
Also remember that if you create a Guest record from a Contact with no email address, then edit that Guest;s Contact record, the Crew Email will remain blank/empty. You will have to update the Guest Email address separately and individually.
This should be a rare situation though, as when importing Contacts it is highly recommended you include as many fields as possible, such as Contact Email. Then when you add that Contact as a Guest, the Contact Email will fill to the Guest Email for you.