When importing mail from Apple Mail, EagleFiler may report a Missing Apple Mail Messages or Missing Apple Mail Attachment error. This indicates that the message had not been fully downloaded to your Mac. You should tell Mail to download the messages and then try the import again. There are several ways to do this:
For a small number of messages that are missing attachments, it’s easiest to open the messages for viewing in Mail. This will trigger Mail to fully download them. You can select the error(s) in EagleFiler’s Errors window and Option-click the Reveal button. This opens the message files in Mail. Once the attachments have loaded in the message windows, you can close the windows and then try the import again.
For a larger number of messages, you can select all the messages to import in Mail and run the Download Apple Mail Messages script. Once this has completed, press the capture key with the same messages selected to import them.
For very large numbers of messages, the script can take a while. A faster option is to Option-drag and drop the entire mailbox to the On My Mac section of Mail’s mailbox list. This will create a local copy of the mailbox with all the messages fully downloaded.
Please note that moving or copying an IMAP message to an On My Mac mailbox will not cause Mail to download the attachments. It may, in fact, mark the attachments as downloaded even though they are missing. And if you then open the message it will be disassociated from the IMAP server so Mail will not be able to fetch the attachments. Thus, it’s best to import the IMAP messages directly from their original mailbox so that EagleFiler can warn you if any attachments are missing and Mail can download them if necessary.
Note: Mail does not allow you to copy special mailboxes such as Sent. However, you can temporarily create a Sent2 mailbox and assign that as the special Sent mailbox in the Mailbox Behaviors settings. Then Mail will let you copy the original Sent mailbox, which now appears with a regular icon. This workaround unfortunately does not work for the inbox.
See also: Importing Attachments From Apple Mail.