Currently, the e-mail address is determined by the exchange server that is specified within the SMTP settings of the PMAdmin site. Password Manager then relies on the information store on the 'mail' attribute for its notifications.
By design. An enhancement request (TF00607360) has been created detailing the feature (Selectable attribute for email notifications).
The product team will evaluate the request and this feature may become available on a future release of the product.
Please refer to this article for updates or contact support referencing the Enhancement Request ID: TF00607360.