Folders becoming read-only after moving a message there

Do you have more than 1 account? If yes, do you see this with all accounts?

Do you see the same behavior using “Message ▸ Move to Mailbox…”?

Try updating to the latest beta (see the Software Update preferences pane).

I have 2 accounts, and the problem only seems to affect one of them. The affected account appears to use Courier-IMAP, the unaffected one is Gmail.

Accessing the command through the menu item behaves in exactly the same way as using the keyboard shortcut: affected folders appear in the list with just the name but no folder icon, and an attempt to move something silently fails.

Updating to the latest beta did not cure the issue, I am still seeing the same problem.

If this helps at all, it seems that in some cases there may be a delay between moving the messages and the folder becoming inaccessible, i.e. the folder works fine for a few minutes, but eventually becomes inaccessible for new writes.

When the mailbox is accessible is it then really synchronized with the server? That is, can you see the messages server-side or with another IMAP email client?

You can create server logs for me as follows:

• Open the Activity Viewer (⌥⌘0). This enables logging.
• Trigger the problem and wait for the mailbox to become inaccessible.
• Use “Help ▸ Send Server Logs” to send me the result.

I sent the logs yesterday evening.

All changes that I can successfully make in MailMate propagate to the server and other IMAP clients. Changes made by other IMAP clients to "read-only" mailboxes do not become visible in MailMate, so it appears the connection is lost both ways there.