Mail click and drop has stopped from Inbox to Folder

A.n' J,

I understand that you're no longer able to drag messages from your inbox to other folders in Mail on your Mac. In such a situation rebuilding the affected mailboxes (both the affected inbox and folders that you're not able to drag to) can help restore your ability to move messages.

Rebuilding a mailbox can take a while depending on how many messages are in the mailbox.

Select a mailbox, and then choose Mailbox > Rebuild.

When you rebuild mailboxes for Internet Message Access Protocol (IMAP) and Exchange accounts, locally stored messages and attachments are discarded, and the messages and attachments are downloaded again from the server to your Mac. Your mailbox appears empty until the download is complete.

Mail (Mountain Lion): Rebuild mailboxes

Regards

Alastair,

Thank you for using the Apple Support Community. Due to the nature of your issue or question you may find more information by using another one of Apple's support resources - https://getsupport.apple.com/GetproductgroupList.action.

All my best