Your customers create accounts on your store's platform, and LoyaltyLion only synchronises some of the data. Because of this, there is no need to contact firstname.lastname@example.org to update a customers' email address.
Once you change the customer's address on your platform, the email in LoyaltyLion will update automatically.
If the customer is updated within your system, and they have the same ID, the next time they sign into LL they will be automatically updated. LoyaltyLion will recognise the changed email from the same customer ID.
Note: this only applies to the customers enrolled to your loyalty program.