Fix incoming email errors in Mail on Mac (OS X)

If incoming email has stopped working in the Mail app on Mac (OS X / macOS) with no error message, the cause is often a corrupted message sitting in your mailbox on the Loopia server. Corrupted messages are typically spam (junk mail) with a size of 0 kB. This guide explains how to find and remove them so the rest of your mail can be delivered.

Why this happens

Mail on Mac can get stuck when it tries to download a corrupted message from the server. Because no error is shown, it can look as though new mail simply isn’t arriving. Removing the offending 0 kB message from the server lets Mail continue downloading new messages as normal.

Step 1: Open Messages on Server

1. Open the Mail app and select your inbox.
2. Press Cmd + I (or choose Mailbox > Get Account Info) to open the account information window.
3. Switch to the Messages on Server tab.

Step 2: Find and remove the corrupted messages

1. Click the Size column header to sort the list by message size.
2. Select any messages that are 0 kB in size.
3. Click Remove From Server.

Step 3: Confirm the deletion

When Mail asks you to confirm, click Remove. The corrupted message is then deleted from the server, and Mail should resume downloading new messages.