A client using Outlook wanted to sync messages he sent using his iCloud account on his iPhone with Outlook. Because iCloud (including me.com addresses) use IMAP, it should work. It didn't so he called Apple support. Apple told him it was not possible to sync Outlook sent items to the iCloud server. I showed him how to do it.

Outlook 2013 / 2016 should pick up the Sent Messages folder automatically and use it instead of Sent Items folder. If it's not using the correct folder, see Sent Messages aren't Syncing to change iCloud to use the sent folder Outlook is using, or use a macro to move Sent Items to Sent Messages folders.

iCloud users who want to sync their sent items with Outlook 2010 or Outlook 2007 can configure Outlook's Sent folder to use iCloud's Sent Messages folder for sent items, or change the phone to use the folder Outlook uses.

To change the folder in Outlook, follow steps 1 and 2 below. See Sent Messages aren't Syncing to change the folder the phone uses.

Step 1: Subscribe to the Sent Messages folder

The Sent Messages folder is not subscribed by default, you'll need to do this step first. Right click on one of the folders in the iCloud folder list and choose IMAP folders....

1. Click Query to list all of the folders on the server.
2. Find and select Sent Messages folder.
3. Click Subscribe.
4. Click Ok to exit the dialog when after selecting and subscribing to the desired folders.

Step 2: Select the Sent Messages folder in Account Settings

1. Open the Account Setting dialog. This is on the File tab in Outlook 2010 and on the Tools menu in Outlook 2007.
2. Double click on the iCloud IMAP account.
3. Click More Settings button.
4. In Outlook 2010, click on the Sent Items tab; in Outlook 2007, click on the Folders tab.
5. Select the option to Choose an existing folder... in
6. Select Sent Messages folder.
7. Click Ok and return to Outlook.

Screenshot from Outlook 2010:

Screenshot from Outlook 2007:

Within a few minutes, the messages you sent from your iPhone should sync to Outlook. Messages you send in Outlook will be available on the iCloud.

Sent Messages aren't Syncing

Use this method if you use Outlook 2013 or Outlook 2016 and it's not using the Sent Messages folder for sent items.

If the messages aren't syncing between Outlook and the iCloud, you need to check settings on the device. Open Settings, select Accounts & Passwords, then select your account. Click on Account email@address > and finally Advanced, then Advanced again on the next dialog. The final dialog lists the folder the iCloud is using for it's special folders. Outlook needs to be using the folder that is assigned to the Sent Mailbox.

Use Sent Messages folder, not Sent Items

If you need to use the Sent Messages folder instead of Sent Items (for example, you use a mix of Mac and Windows computers), and Outlook for Windows is not picking up the correct sent folder, you'll need to use a macro to move the messages as sent messages moved using Rules are not syncing to the server.

This macro, as written, assumes the IMAP account's data file is set as the default data file. It watches the Sent Items folder and moves items added to it to the Sent Messages folder. These moved messages will sync up.

Private WithEvents Items As Outlook.Items
Dim SentItems As Outlook.Folder
 
Private Sub Application_Startup()
' This assumes the IMAP data file is the default data file
    Set SentItems = Session.GetDefaultFolder(olFolderSentMail)
    Set Items = SentItems.Items
End Sub

Private Sub Items_ItemAdd(ByVal Item As Object)
    Set MoveSent = SentItems.Parent.Folders("Sent Messages")
    Item.Move MoveSent
End Sub

If the IMAP data file is not the default data file, you'll need to use the GetFolderPath function from Use a folder in another pst or mailbox. Paste the function at the end of the macros above.

Change the Set SentItems line in Application_Startup to the following (and change the address to your own):
Set SentItems = GetFolderPath("alias@domain.com\Sent Items")

How to use the macro

First: You need to have macro security set to the lowest setting, Enable all macros during testing. The macros will not work with the top two options that disable all macros or unsigned macros. You could choose the option Notification for all macros, then accept it each time you restart Outlook, however, because it's somewhat hard to sneak macros into Outlook (unlike in Word and Excel), allowing all macros is safe, especially during the testing phase. You can sign the macro when it is finished and change the macro security to notify.

To check your macro security in Outlook, go to File, Options, Trust Center and open Trust Center Settings, and change the Macro Settings.

After you test the macro and see that it works, you can either leave macro security set to low or sign the macro.

Macros that run when Outlook starts or automatically need to be in ThisOutlookSession.

Open the VBA Editor by pressing Alt+F11 on your keyboard.

To put the macro code in ThisOutlookSession:

1. Expand Project1 and double click on ThisOutlookSession.
2. Copy then paste the macro into ThisOutlookSession. (Click within the code, Select All using Ctrl+A, Ctrl+C to copy, Ctrl+V to paste.)
3. The macro will run when Outlook starts. To "kickstart" it without restarting Outlook, click in the Application_Startup macro and click the Run button or F8.

More information as well as screenshots are at How to use the VBA Editor