This guide explains how to switch from a POP to an IMAP configuration for the same email account in your email software/client. In fact, for many reasons, it is strongly recommended to use the IMAP protocol instead of POP.

Switching from the POP protocol to the IMAP protocol…

If your email address is already configured with the POP protocol in your email software/client (Mozilla Thunderbird, Microsoft Outlook, etc.), it is impossible to switch to the IMAP protocol directly on the account. Indeed, most common email software/clients do not allow you to modify an existing POP3 account and define it as IMAP instead.

The solution is therefore to add the same email account but with the IMAP protocol in your email software/client and then move your messages and folders from the POP account (on your computer) to the IMAP account (on the email server).

… with Microsoft Outlook

Some versions of Outlook, such as 2016, prevent the simple addition of a second account that would have the same name (identical email address).

To work around this, you need to add the account from the Profiles section:

From there, you can add the additional account, in IMAP:

 

1. Configure the new email account using the IMAP protocol (the same account as the one configured in POP, but this time in IMAP):
   
2. Move one folder at a time by dragging them to the inbox of the new account configured in IMAP:
   
3. Wait for the items to transfer (this may take some time depending on the volume to be transferred to the server); the activity is indicated at the bottom of the window:
   
   

If your POP account kept a copy of the messages on the server (an option that is not recommended and is found in the advanced settings of your Outlook), you may end up with duplicate messages.

… with Apple Mail

Deleting the email account configured in POP will delete the messages it contains. Therefore, it is recommended to disable the POP account instead of deleting it!

Once the POP account is disabled, refer to this other guide to configure your email address in Apple Mail, using IMAP.

Once you have finished, all that remains is to drag the messages in your POP account's folder structure to the new IMAP account's folder structure.