Is it technically possible to setup an email server? Yes it is. You could even do it almost free of charge using open source software postfix, dovecot, CentOS, Ubuntu server,etc. If you get stuck Wash the guru will sort you out. :)

If email communication is critical to the organization i.e you could lose business if emails are not sent or replied to in time, you need to ensure you have a very good internet connection and good power options before you can host a local mail server!

In many African countries(Kenya included), you never get 'super good' internet connections with no downtimes at all. Getting a backup ISP has the tendency to increase an organization's OPEX and you need to have valid points for finance to approve it. Moreover, countries like Ghana and Nigeria are case studies of how blackouts can be a big pain! In South Africa, this almost caused a revolution.

Power and internet connection problems are compelling reasons why you should set up your email server on a cloud service provider. You still have the full control you want plus good uptime.

Short answer : It is possible to setup a local mail server. But not advisable in my opinion unless you have a very good reason for it.

./muya