NS as Exchange replacement: default domain for emails

I have done a fresh install of NS7.3 RC4 on a pc.
Joined it to an existing AD which is on Zentyal 4.3. Purpose here is to see if I can get the NS machine to be an Exchange server using SoGo.
Domain joining went well, and I can now see the list of AD users and groups.
The behaviour is different to Zentyal in that the management panels on the left offer no interaction with SoGo, so I cannot use a GUI to configure anything.
The AD domain is mycompany.lan. The email addresses all need to be mycompany.co.za.

I have created another domain in NS called mycompany.co.za. I then changed some user email accounts to have aliases of user@mycompany.co.za. Default email accounts are all at mydomain.lan. Which is pretty useless as an internet email address.

Perhaps someone can guide me to documentation re how to set the default domain for emails to be mycompany.co.za?

Next issue is I can logon to Sogo web page and find my emails, having setup the pop collection. This works fine.

However I cannot get Microsoft Outlook to connect to the NS box for exchange email account.
NS server name is MAILMAN, I setup Outlook exchange account from a PC joined to the domain, point it at server MAILMAN and Outlook says the Exchange server is offline, cannot be contacted.

I see no specific firewall rule set on NS to allow Sogo-related ports for exchange - is there any setting which would need to be made so I can connect to Exchange services?

Just add this as email domain and add new aliases email for each new email address.

OpenExchange is not supported, you have to use IMAP or try with SOGo ActiveSync support.