Folder: My_Folder was saved as My_x005f_Folder in the next sync. entourage renamed such folder to: My_x005f_x005f_x005f_Folder next time to: My_x005f_x005f_x005f_x005f_x005f_x005f_x005f_Folder and so on until it exceeded the maximal folder length.

Kerio had to avoid this by disallowing the underscore character. Unfortunately, Entourage makes it look like the folder is working perfectly even though it is not being synced.