From: http://shadow-file.blogspot.com/2012/06/parsing-email-and-fixing-timestamps-in.html

timestamp.py

#!/usr/bin/env python
# Based on: http://pastebin.com/ZBq7euid
import email, email.utils, fnmatch, os, re, sys, time
for a, b, c in os.walk("/home/imap-email/store"):
    if "tmp" not in a:
        for d in fnmatch.filter(c, '[0123456789]*'):
            if int(time.time() - (24*60*60)) < os.path.getmtime(os.path.join(a,d)):
                e = os.path.join(a, d)
                f = email.message_from_file(open(e, "r"))
                g = re.sub("\.", "", f.get("Date"))
                h = email.utils.parsedate_tz(g)
                if h is not None:
                    i = int(email.utils.mktime_tz(h))
                    j = 0
                    k = f.get_all("Received", [g])
                    for l in k:
                        m = l.split(";")[-1]
                        n = email.utils.parsedate_tz(m)
                        o = int(email.utils.mktime_tz(n))
                        if (o - i) > (24*60*60):
                            continue
                        j = o
                        break
                    if (j < 1):
                        j = i
                    p = re.compile("([0-9]+)(\..*$)").match(d)
                    if len(p.groups()) == 2:
                        q = str(j)+p.groups()[1]
                        r = os.path.join(a, q)
                        if not os.path.isfile(r):
                            os.rename(e, r)
                            os.utime(r, (j, j))
                            print "Renamed '"+e+"' to '"+r+"'."