transition from G Suite Legacy to iCloud+ custom domain

I have just finished my transition from a G Suite Legacy account (setup in 2013) to iCloud+. Yes you can add up to 5 custom email domains which can be shared with family members. But with family sharing you only get 6 unique email accounts in total. Each account however can be associated with multiple custom domains. So for example, one account could have "me@icloud.com, me@googlecustom1.com and me@googlecustom2.com" but all the email would end up in the same mailbox and all outgoing would be from whatever account you designate to be the primary account. If you need 5 unique email accounts then you will need to use some of the other iCloud+ accounts you have access to (up to 5 others).

You can transfer your email, calendar and contacts from G Suite to iCloud+ as well. Go to https://takeout.google.com/ and select what data you want to include. The calendar and contacts export/import are relatively straightforward but for mail there are a couple of things you should do so that the import works as expected:

1. In your gmail settings in the web browser make sure that "Conversation view" is turned off (otherwise you are going to get inbox and sent messages mixed up together).
2. In Google Takeout deselect all the products then select "Mail" only. Then click "All Mail data included" and uncheck everything except for "Inbox". Hit "OK" and go to the "Next Step" (at bottom of window).
3. Choose "Export once", ".zip" and click "Create export".
4. Repeat the above steps except for mail data choose the "Sent" mailbox.
5. After a few hours you will get an email with download links to your data.
6. Expand the ZIP files and in "Apple Mail" choose "Import Mailboxes" using the "Files in mbox format".
7. Once the import is completed you can move the messages from the import folder to your iCloud email account. [This is a very slow process and it may be safer to only move a couple hundred messages at a time.]

Hope this helps! Let me know if you have any further questions.

My domains are still with the same hosting provider I was using before. To transfer my email to iCloud I only needed to swap the Google and Apple mail settings in the DNS server (Apple sends you an email with everything you need to change).

I am looking to move away from gsuite legacy as well - I am not sure if email migration tools are enabled for iCloud - I have 4 accounts and plan to download all email to local machine and upload for each user once domain is transferred to iCloud. Looks like iCloud allows 5 domains aka domain 1, domain 2 etc and each domain can have a max of 3 accounts. I did not understand family sharing. Since iCloud allows only 3 accounts per domain how do I move 4 accounts from gsuite that are on one domain. All 4 users are currently on iCloud family sharing...

Very helpful thank you. My domain is hosted with secureserver and google would for some reason allow me to renew the domain once every year and not for multiple years. Not sure if you had the same situation. So when you transfer to iCloud+, did you move your domain hosting to another provider or keep it with secureserver (or some other hosting provider). Or is this unique to me.