Online archive (Outlook)
In addition to your personal mailbox or mailboxes another mailbox will be displayed in the folder area of your Outlook:

All e-mails older than one year will be automatically moved from your active mailbox to the online-archive.
Individually created subfolders that exist in your mailbox will be transferred.
To access the online-archive you will need to expand the folder by clicking the arrow:

Inside the online-archive you can search and reply to mails just like in your active mailbox.