Rules in Mail that copy or move messages make them empty

Hi mhutson,

Let's see if the issue still occur after you delete the rule and set it back up for the email account by completing the steps listed here: Use rules to manage emails you receive in Mail on Mac - Apple Support that are also listed below.

1. In the Mail app  on your Mac, choose Mail > Preferences, then click Rules.

To review an example of a rule, select a provided rule, then click Edit. To close the rule, click Cancel.

2. Click Add Rule, then type a name for the rule.

3. Indicate whether any or all of the conditions must be true for the rule to be applied to a message.

4. Specify the conditions.

To use different header fields in conditions, choose “Edit header list” from the bottom of the first pop-up menu. To add your own header, click the Add button  in the Message Headers window.

5. Choose actions to perform on messages that meet the conditions. To specify multiple actions, click the Add button .

You can use AppleScript scripts as rule actions.

6. When you’re done, click OK, then decide to apply rules to existing messages already in mailboxes or to new messages.

You can apply rules to existing messages later by choosing Message > Apply Rules.

If the issue still occurs, let's test the issue in safe mode by completing the steps below that are also listed here: How to use safe mode on your Mac - Apple Support

How to use safe mode

Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:

Apple silicon

1. Shut down your Mac.

2. Turn on your Mac and continue to press and hold the power button until you see the startup options window.

3. Select your startup disk, then press and hold the Shift key while clicking “Continue in Safe Mode.”

4. Log in to your Mac. You might be asked to log in again.

Intel processor

1. Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.

2. Release the key when you see the login window, then log in to your Mac. 

3. You might be asked to log in again. On either the first or second login window, you should see ”Safe Boot” in the upper-right corner of the window.

Best regards