Thanks for your responses.
In the MacWorld link, Step 2 suggests copying all the messages in my current inBox to a folder newly created for this purpose.
I have four POP accounts, and so four inBoxes. Do you suppose I should create four new inBox folders, four new Draft folders, and four new Sent folders?
Why would a new account (albeit IMAP) be messing with my existing POP folders?
The way you read the instructions, all the (dozens of) "On My Mac" folders I have created will not be bothered by this new IMAP account, right?
The link you provided is for those who want to do the opposite of what you want. To add - e.g. Gmail - to Apple Mail...
- Go first to your Gmail account online, and click Settings (the gearwheel top right)
- Click the Forwarding and POP/IMAP tab
- Check the POP Download button
- Make a note of the Gmail server name
Then in Mail...
- Set up a new email account via Preferences
- Enter all the details such as email address, servers, passwords, etc
- (Note that your INPUT server is the Gmail, but your OUTPUT server is your regular POP ISP server)
After that, you should be good to go, and your IMAP Gmail account will be a POP account and can be retrieved via Mail. If you leave your Gmail on their servers also, then you can access it either way.
You can name your mailboxes, and structure them, however you want. On My Mac mailboxes are not associated with any account. You can keep messages from the various accounts separate or not, as you prefer. Inbox is normally used for new incoming messages. Drafts contains messages being prepared for sending. There shouldn't be anything stored long-term in Drafts.
The new account doesn't do anything to the old mailboxes. It's when you deactivate the old POP account that the mailboxes disappear.