hMailServer has some Problems, so far this is true but if you compare it to other MTAs and MDA Projecs t it has some verry unique characteristics other Email Solution cannot provide.
Native Windows Support 32/64-Bit
There are verry few OpenSource Email Servers for
Windows out there. Even with Cygwin or Windows Linux Subsystem for Windows included and MS-Exchange is a Monster requiring 30 GBytes and overly complex and not easy to handle.
MTA and MDA all in one aporoach
I had to Setup various Mailserver Solutions in the last years, mostly on Linux, Unix, MacOS and Windows. Linux Mailservers like Postfix, Sendmail and Exim4 or Qmail are Console Terminal beasts
and you need a lot of Detail Wisdom to get it right.
Most Email Server doesnt have a Forum and have Mailinglists only for support due to lack of good Documentation you have to go into trial and Error
mode to find out if something is even possible.
hMailServer 5 scales extremely well
The ASIO Framework, integrated in hMailServer
can handle gazillions of SMTP/POP3+IMAP Connections where other Packages like Kerio causing 100% CPU utilization and behaving like a Memory hog after just 1k connections. OpenExchange and Zimbra are not full blown own Products rather than Postfix+Dovecot customized builds with some extras and released for (some Linux Distros)only.Mailgate Pro and Mercury32 are Dinosaurs and even worse.
Usability and GUI
hMailServer is compact, just arround 7 MBytes for
the 64-Bit installer which includes allready the GUI which makes it verry straight forward to Setup and even Newbies in the Realm of Email can archieve decent Results in short time.
hMailServer has some Problems but there are coordinated Community efforts going on to get rid of things like DCOM in the Coreserver resulting in a rewritten, reorganized DCOM API for Windows (will be an optional Component) and new Scripting Language (LUA) and finaly Linux, MacOS and even UNIX-Support (Solaris, FreeBSD and Solaris).
Not to mention Multiinstancing
I think its worth it and makes hMailServer (with HCD) even better. But it needs some time because we talking about 200k Lines of Code in the Coreserver itself and we also have to take care of the GUI-Client and compatibility with hMailServer official.