Lots of people have said worthwhile things. Don’t selfhost email for example. While going with an email hoster has been recommended a couple times, which is good and easy, I want to offer an alternative: SimpleLogin (or comparable providers). Essentially a “email alias generator”, it forwards received emails to one or more mail addresses (Google, Hotmail, what have you). It also allows you to connect a domain and then create new inboxes on the fly by simply sending (or telling a service to send) an email to that non-existing inbox. Which is incredibly handy if you’re faced with a situation that demands an email, where you don’t want to give out an actual email.
So say you have the domain doe.com, and you’re in a physical shop at the register, faced with the question if you want to get 10% off by registering for their members club. You can simply give the cashier the email “coupon_walmart@doe.com” (which does not yet exist), the email will be sent, received bei SL, the inbox created and the coupon code forwarded to your Gmail account. Afterwards, you can disable or delete the inbox and never have to worry about newsletters or data breaches. Nifty!
Every one of these boxes also has its own “sent from” address visible in your actual mail account. Which means that you can simply respond to incoming emails, and the recipient will see the mail address they sent a message to. This also means that you can set up filters in your mail account to move messages from certain sender addresses into specific labels, as if they were real separate email accounts.