My grandpa uses Apple mail, backup mayhem...

[JoJoNL]

Hey guys,

My grandpa has all of his emails 'stuck' in Apple mail. 
I'm not an Apple guy (also not a hater, yet), so I thought the usual 'just dragging e-mails to a folder' would work. It doesn't. Ctrl+click and exporting a mailbox also didn't work. After a few google-hours I became apparent that all normal export functions won't work because he has an email archive of about 85Gb... Which is way too big for Apple mail to handle.
So I looked for the *.PST equivalent and found out it's a V4 folder. And indeed, that folder is about 85Gb.

My idea was to upload that folder to my google drive, install mozilla thunderbird on my PC, create a gmail address for him, sync that in Thunderbird and import that V4 folder.

But I wouldn't be posting here if that worked. Thunderbird can import mbox files, but somehow there are no mbox files in that V4 folder, but I can see all folders and subfolders he made. And they are called something like 'inbox.mbox'. All folders end with .mbox.

I'm stuck, hope anyone can help. I just want to put all his e-mails in his gmail, keeping his folder structure.

[maplepants]

iCloud is a normal IMAP email backend. With a mail client like Thunderbird you should be able to sign into iCloud Mail, sign into whatever service you're moving to and then drag and drop between them.

 

You mention though that this didn't work, so what email client were you using when you tried the first time?