Really, true DNS is vital for a home/office server setup.
I don’t understand how some people don’t see it.
First of all there is the “split DNS” feature. To set local addresses for local connections.
In other words, if a mobile client uses “mail.mydomain.com” and asks a DNS for this, the “Internet” DNS (in the bus for example) will properly report the public IP (or even a cname matching a dyndns IP), when if connected in the LAN of the server, the local DNS will instead route than FQDN to a LOCAL IP.
If this is not implemented, many routers are smart enough to not route this to the Internet (only to come “back inside” - which is sometimes also an issue for some cheap routers).
Zentyal (mention this only because it was a recent comparison I made - although Zentyal still “lost” overall), does implement a less-than-full-but-still-ok DNS server. It allows cnames and MX records. Also IIRC allows for setting resolution for more than one domains (thus SOA is also a vital record).
I think the team should really revisit the subject.