Error Message: Mail could not be saved

Question

Just transferred all files from old G4 to new Intel Mac Mini. Mail receives and sends mail without a hitch. However, as I compose messages, I now get a drop down panel that says: Error: The message could not be saved. There are no messages in either the Sent or Draft folders.
My ISP is AOL. Sent messages are stored there, although in Preferences the option to store Drafts or Sent Messages is not checked.
Ron Maier

Answer 1

I don’t know what’s going on here. I’d set up Mail again from scratch, check that things work fine, then import your mail back afterwards as follows:
1. Quit Mail if it’s running.
2. In the Finder, go to ~/Library/. Move (not copy) the entire Mail folder out of there, to the Desktop.
3. In the Finder, go to ~/Library/Preferences/. Locate com.apple.mail.plist and move it to the Desktop.
4. Open Mail and set it up again from scratch. If given the option to import existing mailboxes or something like that, don’t. Just enter the account information and check that everything works fine. Be sure to turn OFF Store messages on the server for all the mailboxes and all the AOL accounts in Preferences > Accounts > Mailbox Behaviors.
5. You’ll have to re-configure all your settings in Mail > Preferences. For spam-related security reasons, the first thing you should do is go to Preferences > Viewing and disable Display remote images in HTML messages if it’s enabled.
6. If Mail works fine now and you had any messages stored in local mailboxes, do File > Import Mailboxes, choose Mail for Mac OS X as the data format, and follow the instructions to import your mail from the old Mail folder that’s now on the Desktop.
Given how ~/Library/Mail/Mailboxes/ is organized in your case, I suggest moving the “On My Mac” folder out of there (e.g. to the Desktop), then separately import the resulting “Mailboxes” and “On My Mac” folders.
If all is well and you don’t miss anything, the files on the Desktop can be deleted, although you may want to keep them for a while, just in case.
Note: For those not familiarized with the ~/ notation, it refers to the user’s home folder. You can easily locate any of the folders referred to in this post by copying the folder path here, doing Go > Go to Folder in the Finder, and pasting the folder path there.