Zoho actually has a free plan for up to 5 users, including a single custom domain. However, they force you to use their web/mobile mail app unless you upgrade to their paid plans which include IMAP/POP and many custom domains. Their paid plans are very reasonable and start out at $1 and $1.20 (5/10GB respectively) a month.
Recently compared Google, Office 365, Proton, Tutanota, Skiff, and Zoho. Surprisingly ended up with Zoho. Actually a decent experience so far, they've definitely upgraded their stack for the better from what I remember it was a decade ago.
Seems 99% reasonable, but the per-message limits make it a non-starter for me. I get why they’re doing it and totally understand where they’re coming from, but the off-chance that an incoming email gets bounced due to no fault of my own (other than subscribing to a higher tier) just doesn’t work for me.
I can also vouch for Migadu. I've been using it for 6-7 years with 4 different domain names because they only charge for usage; not per domain or user. The few times when I contacted support they were also very helpful.
I presume you were grandfathered for free from personal G Suite, but for the rest of us fastmail is actually less expensive than google's offering (though google also gives you Drive space and whatnot).
You could also stick with free Gmail accounts and add on top all addresses and domains you need via gmailify.com[1] for flat $6 per year. It's custom domains extensions for Gmail with own dedicated relays.
I think Fastmail are missing out by not having a "Family" plan for this kind of use case, but just because you're not handing over money doesn't mean Gmail is cheap.
Only one account needs to be a regular account to support custom domains. The others can be basic - 2.50 per month (when paid annually) or $200/year total for 6 users (1 standard + 5 basic)
I did look into that for my family domain but the storage space for the basic plan was so low I ended up sticking with regular accounts. Only two accounts though so bearable. If I was in OP's situation with six family members I probably wouldn't have gone down the FastMail route.
"You can build an account where you mix and match the plan level to each user. For example, you can build a Fastmail Family by adding additional Standard and Basic plans for adults and children."
- https://www.fastmail.com/pricing/
Only one of your accounts needs to be Standard tier ($50/y) to allow up to 100 custom domains. The other 5 accounts can be Basic tier ($30/y) and still use as many custom domains as you give them access to. Total undiscounted cost for your family would be $200/y.
Use the 25% 1Password discount to reduce your total to $150/y. You have the option to extend that 25% discount up to 3yrs and receive an additional discount for paying in advance. Your total for your first 3 years would be $420, then $560 for each 3 years thereafter.
Alternatively, you could consider allowing all your family members use the same Standard account ($105 for the first 3yrs) but with multiple email addresses. Use labels to surface each address for the relevant family member.
In my case, I created a family@surname address for any family business, and a name@surname address for each family member. Each family member has set their Fastmail app to focus on their own address. Yes, technically, they can see each other's email, but it hasn't been a problem. I presume they use throwaway gmail accounts for stuff they want to keep totally private.
We share a specific custom domain for our masked emails and love that feature, especially the 1Password integration although that has some rough edges.
Another happy user of Purelymail here. The GUI is unpolished, but deliverability and reliability have been excellent for me in the few years that I've used it. Unlimited custom domains and inexpensive.
It's not suitable for bulk sending, but for transactional and personal email, I've found it meets my needs.
Be warned, however, that it appears to be a one-man band, and if he goes under a bus...
I'm also a happy user of Migadu. More polished GUI and more features. I've never hit their limits, so not sure how suitable it would be for a medium-sized enterprise. As with Purelymail, it's not intended to be used as a bulk sending service.
Did I read somewhere that Scott is training his brother as a failsafe. Joking aside, I love the service as it is just what I need for not mission-critical stuff, as I tend to board domains and love to experiment with stuff. Would love somewhere else instead of Roundcube, but not sure is there anything modern enough. The only killer feature I need is super fast power search.
Apple has an incredibly cheap option here. If you subscribe to iCloud+ (https://www.apple.com/icloud/), starting at $1/month, you can share one or more custom email domains with up to 6 people total.
I've been using this for a year or so and my family's been happy with it.
An Apple device (iPhone, iPad, or Mac) is required to manage your iCloud+ subscription. It's not intended to work as a web service independent of their products, even if you could use parts of it from other devices.
iCloud+ is primarily cloud backup and storage solution for iPhones. Those two are both very tightly integrated.
The custom email domain is a side feature... but it does work well, and it's essentially free (assuming you want your photos properly backed up... and who doesn't).
I'm not sure if that help article is accurate though - I would think you can subscribe to iCloud+ from their website. You have to go to the website to manage your email domains for example.
You set it up as standard SMTP/IMAP in your email client. There's also a web interface at icloud.com if you want to check your mail there, or set up filters, etc.
I don't think you'd need any Apple gear at all to use it, but make no promises.
I believe they changed this, you can now have an account with multiple levels of users. I believe as long as you have one $5 tier user, you can have additional $3 tier users at your domain.
I have a similar situation and I think that you might be able to have 1 standard account and 5 basic accounts in this situation. Depending on what capabilities the other 5 people need.
Only one account needs to be the $5 one to get the custom domain, the rest of the family can have a $3 / month account and they can use the custom domain too.
I need a custom domain (or three). And I have a family of 6 people.
So that's $5 / user / month = $30 / month = $360 / year.
Unfortunately, that's not justifiable for me. And thus why I'm stuck using Gmail with a custom domain.