IMAP is a very, very cool, underrated technology, but one of the drawbacks is that its resource-intensive when you fire it up the first time. Your Outlook email client has to download all the emails, folders and contents to your local computer, so depending on your internet connection speed, especially if it's slow, syncing can take a while as the sync process is resource-intensive. The usual suspect, in this case, is there is a lot of emails on the mail server or slow internet or a combo of both. You are reading this article because you have set up IMAP on your outlook and it seems to take a long time to sync the folders/emails.
