At my current provider I have an email account with about 7.5GB of emails. Now I'd like to use that domain with iCloud+ going forward. What's the best way to move those 7.5GB to the iCloud email server?
Configure apple mail with your current provider and icloud, then you'll see both in Apple mail and you can start moving emails. I suggest you don't do more than 250 at a time, as it may bug out.
Thanks - with 70k emails that's not the best option. But I found a service called "MailJerry" that is offering a mail transfer through their servers. After almost 24h I'm now 97% done transferring the emails to my iCloud account. So that might be worth a shot for those facing a similar challenge.