I wouldn’t recommend it. I’ve been using the free version for a few weeks and it seems really buggy.
I run a small business also, and I have been using EmClient for about 2 years. For the sake of propriety I purchased the licensed version. In my experience the only true difference between the free version and the licensed version is that the free version is restricted to 2 email addresses (i.e. email@example.com and firstname.lastname@example.org). I haven’t found it to be buggy at all, but I am a computer professional. It is a little bit intense to set up the accounts.
According to our licence agreement, eM Client FREE licence is for non-commercial use only. You’d need to purchase a PRO licence for such use at: https://www.emclient.com/purchase-em-client.