When trying to add a Secondary Email Address to your Box account, some users may see the error "there was an error while trying to add firstname.lastname@example.org to your account".
You will receive this error if the email address you are trying to add is already associated with a Box account.
In order to resolve this issue, please contact Box Product Support. We will help confirm the reason for this error and free up your email address. Please open a case with the email address of your existing account and the email address you are trying to add.