Re: Why not remove the root cause?
it really depends what you are wanting from an on-prem mail server.
If it's simple mail relay then yes there are lots of other options, problem being that relatively speaking there will probably be far more people know Exchange than the various flavours of Sendmail, QMail etc. and can keep it running. Message appliances like Broadcom gateways or Ironports are a better option there.
And Exchange these days is a massive resource hog if you go with MS recommended levels of RAM etc.
If you want all the collaboration bells and whistles that Exchange gives then there aren't really any other enterprise level options.
Notes is still kicking around of course. Have they improved the email client any recently.
It's simply the case that there are still some environments where it is simply not possible to use the cloud for mail, collaboration etc. and that's where the MS stack of Exchange, Skype and SharePoint still has value.