Emailing alarms to external addresses


I would like certain alarms to be emailed to non-users of Ignition to alert external vendors of conditions which they need to address. My question is this - If I set up a user ID for each vendor with multiple contact email addresses, will the alarm go to all of the email addresses attached to the user ID or just the top one? Or, do I need to set up each external email address as a discrete user? Please advise and thanks in advance!