(I'm not affiliated with Fastmail, just a user of their services. Please do research to double-check stuff.)
> I have a number of users at user1/user2/etc@mydomain.com on G Suite. If I started to use Fastmail, could they all continue to use their existing email addresses at Fastmail to send/receive mail, access their historical emails (if I copy those across) etc using whatever client?
Fastmail supports multiple users per domain (and multiple domains btw). For those users it should only need the client updating with details of Fastmail's servers instead of Google's. Then it should work the same.
> And second question: if after this G Suite shutdown in May (or whenever) Gmail is stopped for these users they can presumably still link Fastmail to Gmail? Or would they have to use some other email client?
You'd not be using the GMail app at that point. You would either be using Fastmail's own app or a third party client such as the Outlook app (which is actually very good, only moderately tied to MS, and works with other email providers).
If your users are using GMail on the web they'd switch to the Fastmail site instead and, personally, I think that wipes the floor with the mess that GMail has become.
> Would they each get their own credentials for logging in or would I have to trust them with my "main" Fastmail credentials? I've never used another email provider before.
From Fastmail's user configuration screen: "Each user has their own inbox and login".
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Whatever and whoever you choose, try it first whilst you've still got time. Pick up a really cheap domain name (a random one as it is a throwaway for testing) and start a trial account. Configure a few users, set up the app, and try it out.
Transferring emails is quick with Fastmail, but I wouldn't do that for any kind of test as it is very easy to get a setting wrong and move them from GMail instead of copy them, which makes your trial somewhat more permanent unless you move them back.
Thanks, but Fastmail is $5 per user per month if you want to use your own domain. Not much less than Google's $6 per user per month. I'm going to want between 2 and 4 users, but they're not heavy users and I just know I'm going to be wondering why I'm bothering to pay when I could just create another google account, have access to docs/calendar/drive/etc which I'm apparently not going to have access to even if I am successful in doing the "update to workspace/don't pay for workspace/cancel workspace/keep the workspace accounts in a sort of zombie state" dance.
For what it's worth only the admin user has to be on the Standard tier to use your own domain. The others can be on the basic tier of €3/user/month from where I am.
> I have a number of users at user1/user2/etc@mydomain.com on G Suite. If I started to use Fastmail, could they all continue to use their existing email addresses at Fastmail to send/receive mail, access their historical emails (if I copy those across) etc using whatever client?
Fastmail supports multiple users per domain (and multiple domains btw). For those users it should only need the client updating with details of Fastmail's servers instead of Google's. Then it should work the same.
> And second question: if after this G Suite shutdown in May (or whenever) Gmail is stopped for these users they can presumably still link Fastmail to Gmail? Or would they have to use some other email client?
You'd not be using the GMail app at that point. You would either be using Fastmail's own app or a third party client such as the Outlook app (which is actually very good, only moderately tied to MS, and works with other email providers).
If your users are using GMail on the web they'd switch to the Fastmail site instead and, personally, I think that wipes the floor with the mess that GMail has become.
> Would they each get their own credentials for logging in or would I have to trust them with my "main" Fastmail credentials? I've never used another email provider before.
From Fastmail's user configuration screen: "Each user has their own inbox and login".
---
Whatever and whoever you choose, try it first whilst you've still got time. Pick up a really cheap domain name (a random one as it is a throwaway for testing) and start a trial account. Configure a few users, set up the app, and try it out.
Transferring emails is quick with Fastmail, but I wouldn't do that for any kind of test as it is very easy to get a setting wrong and move them from GMail instead of copy them, which makes your trial somewhat more permanent unless you move them back.