Cloudflare sells domains at cost. If you use apple devices and pay for iCloud+ ($1.99 a month for the cheapest plan), you can get email hosting for your domain for the entire family + a catch all address.

You can run an email host yourself but it is going to cost more in time and effort to maintain than just paying for hosting. It’s not very professional if your messages go to spam due to low reputation or if you miss a message/someone gets a bounce back because the container running your mail server was down and you didn’t realize

Run mail on a custom domain for fun, to learn what it takes, but don’t do it for mail that really matters

If you are just sending notification emails to your own account then you can use SMTP directly to O365 without authentication and it will be delivered as long as it’s being sent within your tenant (if your home IP isn’t in your SPF record it may get delivered to junk however)

This is how we handle scan to email using MFPs in our org. No credentials, or even a mailbox for the outgoing sender, required

I got really long winded on this one sorry. TL;DR yes it would be easier for a big company’s IT department to handle rolling their own nextcloud but larger companies also have more obligations that make it a bit more complicated. A smaller company will need less compute and storage and manhours to manage a next cloud instance and so they can get away with it if they have a great IT person/staff

An on-premises deployment is going to take more manpower to support and maintain than a cloud deployment and an organization of 200 like OP is probably going to have 5-6 IT people who are already stretched thin.

And cloud storage is definitely a cost just like on-premises but it also comes with SLAs with guaranteed uptime and has factors of scale to be able to make delivering uptime, performance, security, and updates a lot more cost effective than rolling your own nextcloud. I’m sure it can be done in a way that is cheaper than $4000 a month or whatever 200 workspace licenses cost but not without taking a shortcut. I wouldn’t run it without a dev, prod, backup and DR server and the salary to maintain those would be just as high.

I’m making assumptions based on my experience and organization’s size and making an educated guess about his friends situation. It could be totally different and they could still have capable hardware and storage from before their cloud migration. I just know that if I was in the same position I would not want to be the one in charge of rolling the company nextcloud when down time is money lost.

I wouldn’t recommend it, a company that size is going to need to guarantee uptime and performance and they are going to need a big cap-ex purchase on servers and storage networks to get it done and get enterprise support and hire staff to maintain it.

For a smaller company that already has the infrastructure to run it, it makes a bit more sense but I wouldn’t recommend it for a small company with nothing or a large company that’s already moved to cloud.

Just one man’s opinion though, I don’t know the situation.

I am already paying for iCloud+ so I use their service with my domain. It gets the job done.