Could anyone please advise what if any are the issues with setting up the autodiscover to broadcast outside the LAN. I am trying to set up some non domain clients so that they can access exchange over the internet but without autodiscover set up this can be challenging. I cannot seem to get a simple answer out of my tech support as to what issues there are.

Hi, If you talk about autodiscover for external client then it must be secure thru SSL. For non domain joined clients or clients that are not able to directly access the domain, Outlook is hard coded to find the Autodiscover end point by looking up autodiscover URL. This means that to service clients in this scenario we must provide connectivity to one of these URLs. Security Concern: On the surface this should not be hard; but this connection is made over SSL and requires a valid certificate.Anil

So there is no way for people to spam the autodiscover addresses to find out login credentials etc?

I would use a third party for SSL. Anything is possible.