I get the above error message for two of my four configured e-mail accounts.

Some history: this morning, while checking mail, I got an error "Failed to move message to trash" in kmail. From that point on I couldn't read any mail anymore until I restarted akonadi. The next attempt to remove a mail message got me in the exact same situation.

So I stopped quit kmail, stopped akonadi and then removed the complete ~/.local/share/akonadi directory to start from a fresh akonadi database.

Upon the next start of kmail, only two of my four accounts were still visible in the mailbox list view. Akonadi still shows the configuration for all four mailboxes.

However, when attempting to use the two failing imap configurations, I get this error:
List failed, server replied: A000007 NO Permission denied

I'm pretty sure this is an akonadi only problem, because I can access these mail accounts perfectly fine from another mail client (I have tried Thunderbird).

I have also tried to recreate one of the accounts, but that doesn't make any difference. The error remains.

Reproducible: Always

Steps to Reproduce:
I'm not sure what to write, so I'll just write what I did
1. Quit Kmail, then stop akonadi
2. Delete ~/.local/share/akonadi
3. Restart akonadi
Actual Results:  
Two out of four imap mail accounts don't show up anymore in kmail.

Expected Results:  
Akonadi should be able to connect to all 4 e-mail addresses.

I may be relevant that of my 4 mail accounts 3 are on the same mailserver, so other than username/password, they use the exact same configuration. Only one of these is currently working, although I don't see any configuration error.

There is an akonadi server error log with exactly one line:
Error during executing query "INSERT INTO CollectionTable (remoteId, remoteRevision, name, parentId, resourceId, cachePolicyInherit, isVirtual) VALUES (:0, :1, :2, :3, :4, :5, :6)" :  "Duplicate entry '60-Kobalt' for key 'CollectionTable_parentAndNameIndex' QMYSQL3: Unable to execute statement"