External Users won’t receive confirmation emails

Hi there, 

We’re looking at setting up Bookings as a way to passively generate leads from our site where they can automatically schedule a meeting with our Sales team if they know what they’re looking for.

When testing everything out, it would only send email confirmations to internal users, and would not deliver to external emails (I used both my personal gmail and hotmail). I posted this on the general forums and had IT look at the Admin settings, which were change to what their recommendations were but it did not help. For reference, they suggested making the calendars visible externally and also a general settings change that made sure external bookings were not blocked.

 The error we’re getting is still that tye confirmation email and meeting being sent out is an undeliverable message to the client. Any way to fix this so I can pass this along to IT as they look to find a solution?? 

Thank you!