IMAP folders in Windows Outlook – Read it to know more about it.
An IMAP is a major and mostly used form of protocol used by clients like Outlook and almost all other email clients and email providers.
There are two major ways of retrieving emails and folders – POP and IMAP. In most cases today, IMAP is significantly more preferred than POP as it is more modern and most sophisticated protocol that adds a lot more features. We have covered IMAP and POP protocols in depth in our previous articles. Today, we are going to discuss something more specific related to IMAP folders, and that is in respect to specific folders instead of an entire email account.
IMAP Folders
When you add an IMAP email account, Outlook retrieves all emails and the folders and their hierarchy as it is stored on email servers. Those folders are visible on the left “folder pane” side, as shown below:

When you add a new IMAP email account in Outlook, all the folders get retrieved from the servers and are stored in the computer inside OST files, unless you specified otherwise.
But there are also options to disable the specific IMAP folders and essentially stop them from synchronizing between servers and locally. Whatever that was downloaded will still remain stored for offline use.
To do this, first select the folder, and then go to the “Folder” tab on the ribbon and click on “IMAP folders.”
IMAP Folders in Outlook Windows

The ‘IMAP folders” dialog box will open, like this:

The list of all the IMAP and subscribed folders will be empty at first. Click on “Query” to let Outlook query the database and the servers to retrieve the list of all the folders. To check the folders that you have subscribed to (meaning, it syncs across the servers and locally), click on the “Subscribed” tab next to “All.”
Subscribe / Unsubscribe IMAP folders
Once the query is finished, you can click the folder that you want to either subscribe or unsubscribe and then click the “Subscribe” or “unsubscribe” button on the right.

Subscribing simply means that the folder is now synced with the servers and thus meaning it is an IMAP folder. Unsubscribing stops the sync and makes the folder non-IMAP based folder.
Note that some folders cannot be changed like Drafts and Outbox and Sent. These folders are called “Special Folders” and must always be IMAP.
One of the benefits of disabling IMAP based folders is saving space on your computer and also reducing the sync time. The kind of emails or folders that you do not need to access from anywhere and are not frequently used can be “unsubscribed” and you will stop receiving mails from them in Outlook. Note that the folder will still receive the emails on the server.
You can also choose to display only IMAP folders inside the “Folder Pane” to avoid any sort of confusion. This way you cannot see those folders which are unsubscribed, which isn’t a great deal because you are unlikely to need them frequently anyway.