Hello, my name is Dmitry, I'm experienced Linux admin for a few years. Have several email servers running for my personal and business needs, it's not a big deal to setup another one for you. I'll be using iredmail bundle, it will allow both of us to a) setup the mail solution quickly and without a hassle; b) support and maintain this system in future, even without me, you can ask someone to help you on freelance or even get a paid support from iredmail developers (they offer).
This solution is pretty stable, having my servers running for months and didn't face any problem so far. What do you think? We can chat to discuss this project more, you can give me more details and I'll advise you on the estimates.
Thank you for reading this, have a nice day and stay safe.