Message has changed

Question

I just spent a lot of time cleaning up my inbox by setting up rules and moving messages to mailboxes on my mac rather than leaving them on the server.
I made mailboxes and sub-mailboxes. I used the rules to move messages. Some I moved manually.
Most of them are fine, but others have changed. Instead of the mesage, I get a note that says "The message from xxxxxhas not been downloaded from the server. You need to take this account online in order to download it.
But that message is no longer on the server as I have moved it to my mac. I am online with the account. I don't understand what has happened to the message.

Answer 1

This is one of the many bogus error messages in Mail that have absolutely nothing to do with what the problem really is. Don’t try to make sense of it. What the error message really means in the case of Mail 2.x is that the *.emlx file associated with the message isn’t where the index says it should be.
Mail has quite a few bugs & glitches when it comes to managing and/or renaming custom mailboxes. Here’s a recent example that describes a problem similar to what may have happened to you:
Crazy problem moving nested folders
In order to fix the problem, proceed as follows:
1. Quit Mail if it’s running.
2. In the Finder, go to ~/Library/Mail/. Make a backup copy of this folder, just in case something goes wrong, e.g. by dragging it to the Desktop while holding the Option (Alt) key down. This is where all your mail is stored.
3. Locate Envelope Index and move it to the Trash. If you see an Envelope Index-journal file there, delete it as well.
4. Open Mail. It will tell you that your mail needs to be “imported”. Click Continue and Mail will proceed to re-create Envelope Index -- Mail says it’s “importing”, but it just re-creates the index if the mailboxes are already in Mail 2.x format.
Note: For those not familiarized with the ~/ notation, it refers to the user’s home folder, i.e. ~/Library is the Library folder within the user’s home folder.