After you’ve set up an IMAP account in Apple Mail on Mac OS X, there’s an additional step needed to to keep Mail folders in sync with other programs or devices that might connect to the mailbox.

By default, Apple Mail won’t try to store sent or deleted messages on the server. It will try to store them on your Mac, and will sometimes show error messages when doing that, including an error complaining that a deleted message “could not be moved to the mailbox (null)”.

On this page:

• How can I tell what needs fixing?
• Telling Apple Mail to store “Sent” and “Trash” on the server
• What should it look like when I’m done?
• What if there are extra folders left over, like “Sent Items” or “Deleted Items”?
• What if the special folders aren’t visible?
• Moving other folders out from under the Inbox

How can I tell what needs fixing?

You can tell this needs fixing when your “Sent” and “Trash” mailbox folders show with plain icons, like this with the plain icons under the “Inbox”:

Or like this, with them in a separate section:

Or even like this, where the “Inbox” has plain folders, but there’s also a strange extra unusable “address@example.com” section under “Sent” or “Trash”:

The plain folder icons indicate that Apple Mail doesn’t consider them to be special folders that it should use for storing sent mail or deleted mail. That means that when you send or delete mail on your Mac, you won’t be able to see the messages on other devices like an iPhone.

Telling Apple Mail to store “Sent” and “Trash” on the server

To fix this problem, highlight the plain Sent folder for the new mailbox by clicking once on it. (Make sure you highlight the plain folder, not the “Sent” that already shows the paper airplane icon.)

Then click the Mailbox menu and choose Use This Mailbox As > Sent Mailbox, like this:

(If the “Sent Mailbox” option is greyed out, make sure you’ve first clicked the plain “Sent” folder as shown in the pictures at the top of this page. If you don’t see the plain folder, it may be hidden two levels deep inside the Inbox — expand a folder named with your account if you see one.)

Repeat for the Trash folder by clicking the plain Trash folder, then choosing Use This Mailbox As > Trash Mailbox.

(If you see a “Drafts” folder, you can do the same for that one. However, Apple Mail may not create a Drafts folder until you actually write a draft email message.)

After doing this, the Sent and Trash folders will move to the global “Sent” and “Trash” sections with custom icons of a paper airplane and a trash can. There will no longer be separate, plain icon copies of these folders in the usual folder list.

By the way, if you have multiple accounts in Apple Mail, you may need to click a small triangle next to the global “Sent” or “Trash” sections to see the matching folder. (The triangle may not appear until you send your first message in the case of “Sent”, or until you delete your first message in the case of “Trash”.)

What should it look like when I’m done?

When you’ve done this, all of the “Sent” and “Trash” folders should change to special icons, like this:

Or like this, if you have multiple addresses in Apple Mail:

What if there are extra folders left over, like “Sent Items” or “Deleted Items”?

Apple Mail has an annoying habit of creating extra folders with names like like “Sent Items” and “Deleted Items”, in addition to the “Sent” and “Trash” folders.

If you’ve set things up as described above, any “Sent Items” or “Deleted Items” folders should be empty, with a plain icon, and safe to delete if you want to keep things neat:

• Click on the folder you don’t want
• Make sure it’s completely empty (if it isn’t, you can drag messages to the place you really want to keep them)
• Click on the empty folder while holding down the “control” key
• Choose Delete Mailbox… from the menu that appears
• Confirm that you want to delete the folder

This will permanently delete the folder’s contents, so make sure that it really is empty.

What if the special folders aren’t visible?

A bug in some versions of Apple Mail can make the “Trash” and other folders invisible to start with, making it impossible to select the plain icon version of them to enable the “Use This Mailbox As” menu option.

To fix this, first make sure you’ve tried sending a message and deleting one. That will sometimes make the matching folder appear. If that doesn’t help:

• Click on the “Inbox” while holding down the “control” key
• Choose New Mailbox… from the menu that appears
• Create a folder named Test in the “address@example.com” location
• Click on the “Inbox” while holding down the “control” key again
• Choose Synchronize “address@example.com” from the menu that appears

The “Test” folder should appear, along with the missing “Trash” and other folders. You can then follow the instructions above for the “Use This Mailbox As” menu. When you’re finished, delete the “Test” folder:

• Click on the “Test” folder while holding down the “control” key
• Choose Delete Mailbox… from the menu that appears
• Confirm that you want to delete the “Test” folder

Moving other folders out from under the Inbox

If you’ve created other folders beyond the special “Sent” and “Trash” folders, they may appear under the “Inbox” icon, or they may appear in their own separate section at the bottom of the sidebar.

If you want to move them from one location to the other, you can change a setting in the Apple Mail preferences:

• Using the menu bar at the top of the screen, click Mail, then Preferences.
• Click Accounts (the blue "@" sign) along the top of the window if necessary.
• Click the address@example.com account in the left “Accounts” column if necessary.
• Click the Advanced tab.

The settings will look something like this:

The important part here is the “IMAP Path Prefix”:

• If the IMAP Path Prefix is blank, folders will show up under your Inbox.
• If the IMAP Path Prefix is INBOX, folders will show up in a separate section.

You can change the IMAP Path Prefix to choose whichever behavior you prefer.