Exchange 2013 C17 Set Authenthication Mapi Https

Hi ,

We have enabled Mapi over HTTP and its set to true.
Internal all working but external i forgot to set the outlook.mijdomain.com in it so i did sucsesfull.

Now i need to set per server the authentication method as its asking from outside a password to fill in.

What will be the correct command and correct or stanaard authenthication settings?
Many thanks.

It should be something like ?

Set-MapiVirtualDirectory -Identity "Servernameexchange01\mapi (Default Web Site)" -ExternalUrl https://outlook.mydomain.com/mapi -IISAuthenticationMethods Negotiate
(not sure)
Many thanks.