Backup iMap account

[smartarts]

I am a web host. I have client who us currently using his email account as iMap - I need to change him over to POP3 due to storage restrictions on my server.
He is using Office 365 for Buisness.
I want to make a backup of all his individual email folders along with any attachments. Then remove the iMap account and set it up again as POP3 and then import all this mailboxes back in again.
I assume Outlook 365 has this capability. Any tips would be greatly appreciated.

 

[smartarts]

just to clarify

I have a large virtual server setup that I have been using for many years with a reasonably large customer base for a 1 person operation (about 450 email accounts over 40 or so domains) - I have to pay for more storage so I don't use IMAP - all my clients are happy using POP3

Some of my clients get very large attachments (yes I have suggested dropbox & other methods but they are set in their ways) so the size of their accounts grows quickly

I don't have an exchange server

I have explained how it works to any/all clients who ask including this guy

This particular guy has about 20 sub folders where his email are stored on the server - just removing IMAP setting it back up as pop won't download all those emails nor will it download his sent box

That why I have posed the question about using Office 365/Outlook to create a backup of all emails, folders & attachments so that I can re-instate them once I remove IMAP and create POP3