Unknown namespace

Error: Unknown namespace

This error indicates that your IMAP server is not RFC-compliant.

For example, we find that some IMAP servers:

  1. Reject the creation (or retrieval) of folders with special characters (such as "*", "-", etc.) or leading/trailing spaces.
  2. Reject the creation of folders, unless located under the inbox folder (i.e., cannot create "/A" - must create as "/Inbox/A").
  3. Reject the creation of folders with certain reserved names (i.e., "junk mail", "sent mail", etc.)​.


We recommend the following:

  1. Identify the category of problem: special character, folder location, reserved name.
  2. Identify if the error is with the Source or Destination (check errors in MigrationWiz).
  3. Consider renaming folders at the Source to avoid special characters.
  4. Connect an email client (Outlook, Thunderbird) to understand limitations:
    1. Connect with Outlook or Thunderbird using IMAP.
    2. For example, if creating folder /A failed, try creating this folder at the root.
    3. Check to see if an error is displayed to you by the email client.
  5. Consider remapping folders:
    1. Edit your project and reveal Advanced Options. All Folder Mapping must added as written.
    2. In Support Only options, enter FolderMapping="^->INBOX/" FolderMapping="INBOX/INBOX->INBOX"
    3. This will ensure that /Inbox remains mapped to /Inbox, but that /A gets mapped to /Inbox/A
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