This guide explains how to delete folders that appear grayed out in the Web app Mail Infomaniak (online service ksuite.infomaniak.com/mail) or in some email software/clients such as Apple Mail, Mozilla Thunderbird, or Microsoft Outlook.

Ghost folders

Some email software/clients like Microsoft Outlook allow you to create subfolders of non-existent folders. For example, it is possible to create the folder /abc/klm/xyz while the folder "klm" does not exist.

On Mail Infomaniak or in other software, ghost folders like the folder "klm" appear in gray and cannot be deleted directly as they are only "paths" to a real subfolder.

To delete these ghost folders, it is necessary to delete their subfolders first (in this example: xyz).

Stubborn folders

If, when consulting your Infomaniak email address on Outlook, ghost folders persist or reappear instantly after deletion, here are the technical procedures recommended by Microsoft to force synchronization:

1. Force Outlook folders reset

Sometimes, Outlook's local folder table is corrupted. A simple command can often fix this without deleting anything:

• Close Outlook completely.
• Press the Windows + R keys on your keyboard.
• Type outlook.exe /resetfolders and validate (this restores missing or corrupted folders from the server).

2. Reset the IMAP cache (.ost)

If the problem persists, forcing Outlook to rebuild its local database is often the most effective solution:

• Close Outlook.
• Access the folder: C:\Users\[Your Username]\AppData\Local\Microsoft\Outlook.
• Identify the .ost file with the name of your Infomaniak address and delete it (or rename it to .old for safety).
• Restart Outlook. The software will redownload all your messages and folders properly from the Infomaniak servers.

3. Use the MFCMAPI tool (Advanced Level)

MFCMAPI allows you to access the MAPI structure of your mailbox directly to delete what the standard Outlook interface refuses to touch:

• Download the latest version of MFCMAPI from GitHub (Official Source).
• Launch MFCMAPI.exe and go to Session > Logon. Select your Outlook profile.
• Double-click on your Infomaniak mail account in the list.
• In the new window, expand Root Container (or Root - Mailbox), then IPM_SUBTREE.
• Locate the problematic folder. Right-click and select Delete folder.
• Warning: In the dialog box, try simple deletion first. If this fails, retry by checking DELETE_HARD_DELETE (permanent deletion at the server level).

4. Final verification via Webmail

If a folder is deleted in Outlook but keeps reappearing, check on the Infomaniak Web Mail app if the folder is present, and delete it first via the Web interface, then apply step #1 (resetfolders) in Outlook.