diff --git a/Lib/imaplib.py b/Lib/imaplib.py
--- a/Lib/imaplib.py
+++ b/Lib/imaplib.py
@@ -120,6 +120,7 @@
 _Literal = br'.*{(?P<size>\d+)}$'
 _Untagged_status = br'\* (?P<data>\d+) (?P<type>[A-Z-]+)( (?P<data2>.*))?'
 
+_Atom_Specials = re.compile(r'[\(\)\{ \%\*\"\\\]]')
 
 
 class IMAP4:
@@ -941,7 +942,10 @@
 for arg in args:
 if arg is None: continue
 if isinstance(arg, str):
+ if _Atom_Specials.search(arg):
+ arg = '"' + arg + '"'
 arg = bytes(arg, self._encoding)
+
 data = data + b' ' + arg
 
 literal = self.literal
diff --git a/Lib/test/test_imaplib.py b/Lib/test/test_imaplib.py
--- a/Lib/test/test_imaplib.py
+++ b/Lib/test/test_imaplib.py
@@ -10,6 +10,7 @@
 import socketserver
 import time
 import calendar
+import re
 
 from test.support import (reap_threads, verbose, transient_internet,
 run_with_tz, run_with_locale)
@@ -142,7 +143,7 @@
 except StopIteration:
 self.continuation = None
 continue
- splitline = line.decode('ASCII').split()
+ splitline = re.findall(r'[^"\s]\S*&#124;".+?"', line.decode('ASCII'))
 tag = splitline[0]
 cmd = splitline[1]
 args = splitline[2:]
@@ -265,6 +266,23 @@
 self.assertRaises(imaplib.IMAP4.abort,
 self.imap_class, *server.server_address)
 
+ # Issue 13940: space in mailbox names
+ @reap_threads
+ def test_create_with_space(self):
+ class CreateHandler(SimpleIMAPHandler):
+ def cmd_CREATE(self, tag, args):
+ if args[0] == '"name with space"':
+ self._send_tagged(tag, 'OK', 'CREATE completed')
+ return self._send_tagged(tag, 'BAD', args[0])
+
+ with self.reaped_server(CreateHandler) as server:
+ client = self.imap_class(*server.server_address)
+ client.state = 'AUTH'
+ typ, data = client.create('name with space')
+ self.assertEqual(typ, 'OK')
+ self.assertEqual(data[0], b'CREATE completed')
+ client.shutdown()
+
 class UTF8Server(SimpleIMAPHandler):
 capabilities = 'AUTH ENABLE UTF8=ACCEPT'
 
</div><div class="naked_ctrl">
<form action="/index.cgi/contrast" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="https://bugs.python.org/file41037/issue13940.patch">(-&gt;オリジナル)</a>
/ <label>アドレス: <input type="text" name="naked_post_url" value="https://bugs.python.org/file41037/issue13940.patch" size="22" /></label> <label>モード: <select name="naked_post_mode">
<option value="default">デフォルト</option>
<option value="speech">音声ブラウザ</option>
<option value="ruby">ルビ付き</option>
<option value="contrast" selected="selected">配色反転</option>
<option value="larger-text">文字拡大</option>
<option value="mobile">モバイル</option>
</select>
<input type="submit" value="表示" />
</p>
</form>
</div>