<p>It's likely happening when the root of the maildir has new/tmp/cur.</p>

<pre><code>OfflineIMAP 6.5.7
  Licensed under the GNU GPL v2 or any later version (with an OpenSSL exception)
Account sync hermes@whatever.org:
 *** Processing account hermes@whatever.org
 Establishing connection to imap.whatever.org:993
 Creating folder /[hermes@whatever.org-Remote]
 ERROR: Creating folder  on repository hermes@whatever.org-Remote
  Folder '/'[hermes@whatever.org-Remote] could not be created. Server responded: ('NO', ['unsupported folder name'])
 ERROR: Folder '/'[hermes@whatever.org-Remote] could not be created. Server responded: ('NO', ['unsupported folder name'])
 *** Finished account 'hermes@whatever.org' in 0:00
ERROR: Exceptions occurred during the run!
ERROR: Creating folder  on repository hermes@whatever.org-Remote
  Folder '/'[hermes@whatever.org-Remote] could not be created. Server responded: ('NO', ['unsupported folder name'])

Traceback:
  File "/usr/lib64/python2.7/site-packages/offlineimap/repository/Base.py", line 242, in sync_folder_structure
    src_repo.makefolder(dst_name_t)
  File "/usr/lib64/python2.7/site-packages/offlineimap/repository/IMAP.py", line 434, in makefolder
    OfflineImapError.ERROR.FOLDER)

ERROR: Folder '/'[hermes@whatever.org-Remote] could not be created. Server responded: ('NO', ['unsupported folder name'])

Traceback:
  File "/usr/lib64/python2.7/site-packages/offlineimap/accounts.py", line 263, in syncrunner
    self.__sync()
  File "/usr/lib64/python2.7/site-packages/offlineimap/accounts.py", line 329, in __sync
    remoterepos.sync_folder_structure(localrepos, statusrepos)
  File "/usr/lib64/python2.7/site-packages/offlineimap/repository/Base.py", line 242, in sync_folder_structure
    src_repo.makefolder(dst_name_t)
  File "/usr/lib64/python2.7/site-packages/offlineimap/repository/IMAP.py", line 434, in makefolder
    OfflineImapError.ERROR.FOLDER)
</code></pre>

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