Hi Craig,

The first thing you should check is what your default reply address in Admin> Channels> Email is, that gets set to Zendesk generated account address by default when the account is created, but it can be updated to make one of your connected addresses the default instead (assuming that you've set up the DNS records for the emails to allow Zendesk to send for them). Just hover over the email addresses to see if it's the default or if you have the option "make default".

There is an app that you can use to set different default reply addresses for different groups, so you can get closer to what you want overall by using the Select An Address app to make sales and tech support groups have different default reply addresses. We have more on configuring that app in Installing and using the Select an Address app.

The limitation here is going to be that the app only controls the replies sent after the ticket is created (the app needs the ticket to already exist before it updates information). The first auto-reply when the ticket is created is always going to come from your default reply address, but this would let you control which address all agent responses and other ticket notifications came from. It would also let your team manually update a reply address if something had either been sent in on the wrong form or needed to be redirected to another team.

I hope that helps!