This looks like a server-side bug.
GetFolderList(folderName) method is called to list the contents of the specified folder, it first issues '
LIST "" FolderName' command to list the specified folder in its root location, and determine the folder hierarchy delimiter used by the folder.
Next, once the delimiter has been determined, the method issues '
LIST "" "FolderName[DELIMITER]%" (with "[DELIMITER]" replaced by the folder delimiter used by the server - usually '/', '\' or '.').
According to the log you posted, this works fine for "Drafts", "Junk" and other folders, but the server has trouble with "Inbox", where it fails during the first step (determining the delimiter). And unfortunately, the failure is identical to one that occurs when the specified folder does not exist.
If you need to fix this, please contact the server vendor.
As a workaround, call
GetFolderList("Inbox/%") on this server instead of
GetFolderList("Inbox") to skip the delimiter-detection part of
GetFolderList. (Make sure not to apply this on other servers which could use different folder delimiters.)