Staging emails can be sent to users identified by roles, specific email addresses, and the "creator" of the staging repo. If any one of these collected addresses is invalid syntactically, the entire email sending fails. The message logged:
Some client side validation should be performed on the collected addresses before sending. If there are any addresses left after striping out the bad ones, continue the send attempt to these 'good ones'. Log at WARN all stripped addresses so an admin has a chance to correct this.