You're limiting your options by insisting to have both app and email hosting with the same company. My suggestion is to investigate them separately.

For app hosting, fire and forget (Heroku, Amazon Elastic Beanstalk), shared hosting (like Webfaction and many others), VPS/dedicated server (like AWS EC2, Digital Ocean and many others).

Managed options will take a lot less effort and knowhow to keep a production app running, but cost more. Your own server (VPS) will get you more resources for the same price, but you'll have to configure and maintain everything yourself (app server, static files, database, load balancing, backups and recovery, monitoring, upgrades, security, performance, scaling, etc).

For company email, Office 365, Google G Suite, Rackspace Mail. Maybe Amazon WorkMail (I only know it exists).

Edit: I misunderstood that you're looking for email service. If you want to run your mail server yourself, you need 1) a computer you control (VPS/dedicated) and 2) to know what you're doing. Unless you have a good reason to do that, I suggest you outsource it and get on with your business.