I use Google Apps now because the pricing for Googlers is too good to pass up (practically free, 48 times cheaper than iCloud+), but before that when I was being frugal I just set up gmail with my own domain (no payment required).

Instructions: https://paulonteri.com/thoughts/how-to/custom-domain-with-gm...

If your org is more than one person, this might get unwieldy.