How to fix error while moving messages in Apple Mail

A common problem with Apple Mail (also often called Mac Mail) is the “error occurred while moving messages to mailbox (null)” error. This problem occurs when folders for the Drafts, Sent, Junk, or Trash mailbox are not assigned. This error most commonly occurs when deleting messages and the Trash mailbox has not been assigned, but happens whenever messages are moved without the folders being assigned. Here’s a screenshot of the error:

Fixing the Error with Moving Messages in Apple Mail

In order to use these instructions, you will need to have added an email account into the Apple Mail client.

1. Log into the Apple Mail Client.
2. 

   Scroll down to your newly added mail account. Click on the drop-arrow to see the Drafts, Sent, Junk, and Trash folders, then click on the Drafts folder to highlight it.
3. 

   In the Menu at the top of the screen, click on Mailbox, then scroll down to Use This Mailbox As, then click on the Drafts Mailbox. This will assign the Drafts folder in the client to the corresponding server folder.
4. Repeat this action for all of your folders (Sent, Junk, and Trash), and make sure to click on the respective folder assignment. As you add these folders, you will see the email account name added for each option.

When the folders have been assigned, the error will no longer appear when sending, moving, and/or deleting messages.