Migrating From POP to IMAP
Here are some tips to help you make the switch from POP to IMAP:
Avoid Duplicate or Missing IMAP Messages
Once you have your IMAP account setup, be sure to remove your POP account from any regularly scheduled and manual email checks. This will prevent duplicate or missing messages when you use IMAP that are caused by the confusion of using both systems together.
Copy POP Folders and Messages to IMAP Server
Before you delete your POP account, you may wish to copy some or all of your POP folders and messages to the IMAP server. Doing so will allow you to see them in Web Mail and with an IMAP email program on another computer or device; thus, taking advantage of IMAP's benefits.
Update Email Rules
If you use any sort of email rules (filters), be sure to edit them so that they point to your folders on the IMAP server.