Apple Mail messages disappeared after IMAP deletion + local move failure (no disk space) – emlx files still exist but appear empty

Question

I am trying to recover my Apple Mail inbox on macOS Yosemite (Mail v8) after a series of events caused all messages to disappear from the application, even though the raw files are still present on disk.

What happened

1. The Inbox was accidentally deleted on an iPhone, which removed the IMAP messages from the server.
2. On my MacBook (offline at that moment), the emails were still present locally inside Apple Mail.
3. I tried to move the messages from the IMAP Inbox into a local "On My Mac" mailbox to save them.
4. During this move, the Mac ran out of disk space.
5. The move operation aborted, and afterwards, the original Inbox inside Apple Mail appeared completely empty.
6. However, on the filesystem, the raw (emlx and Attachments) mail files still exist.

Where the files are located

The messages are stored in Apple Mail’s IMAP local cache at:

~/Library/Mail/V2/<IMAP-ACCOUNT>/INBOX.mbox/

with a structure like:

INBOX.mbox/
└── <GUID>/
 └── Data/
 └── 0/
 └── 1/
 ├── Messages/
 └── Attachments/
 └── 2/
 └── 3/
 ... (many more)

Inside these various Messages folders, there are thousands of:

• *.emlx
• *.emlxpart
• *.partial.emlx

What I am seeing

• Each .emlx file has a normal file size (for example, several KB or more).
• But when I open them directly on macOS, they appear empty in Apple Mail and show no message text.
• If I manually rename an .emlx file to .eml and open it on Windows or in another mail program, the message content is fully visible.
• So the file content is still there, Apple Mail just refuses to display it.

Current state

• I now have plenty of free disk space again.
• I still have the entire original INBOX.mbox folder.
• Apple Mail refuses to show or rebuild the messages.
• Rebuilding the Mail index (Envelope Index* files) did not help.
• The data clearly exists in the .emlx, but Apple Mail does not see it.

My question

How can I restore the mailbox so that Apple Mail recognizes and displays the messages again? I would like to either:

1. Rebuild the original IMAP Inbox locally in Apple Mail,
2. or recreate a valid local mailbox from the .emlx files,
3. or convert this structure into a proper .mbox file that Apple Mail can import.

At this point, I simply want a clean mailbox (local or mbox export) so I can later upload the messages to the IMAP server again.

Additional notes

• macOS: Yosemite
• Mail.app version: 8
• IMAP account
• No Time Machine backup
• The issue started after the disk ran out of space during a move from IMAP to a local mailbox
• The raw files still contain the real message data (verified by renaming to .eml)

• Linc Davis: You say you have no Time Machine backups. Does that mean you have no backups at all? If so, do nothing else until you've backed up. Using a computer with no backups is a rolling data-loss emergency.