diff -r 406c6fd7e753 Lib/imaplib.py
--- a/Lib/imaplib.py	Sun Mar 17 21:53:48 2013 -0400
+++ b/Lib/imaplib.py	Mon Mar 18 21:49:09 2013 -0700
@@ -24,6 +24,7 @@
 
 import binascii, errno, random, re, socket, subprocess, sys, time, calendar
 from datetime import datetime, timezone, timedelta
+from io import DEFAULT_BUFFER_SIZE
 try:
     import ssl
     HAVE_SSL = True
@@ -1244,6 +1245,7 @@
         self.sock = None
         self.file = None
         self.process = subprocess.Popen(self.command,
+            bufsize=DEFAULT_BUFFER_SIZE,
             stdin=subprocess.PIPE, stdout=subprocess.PIPE,
             shell=True, close_fds=True)
         self.writefile = self.process.stdin