diff --git a/cmd/mailhash/mailhash.go b/cmd/mailhash/mailhash.go
new file mode 100644
index 0000000..e94106c
--- /dev/null
+++ b/cmd/mailhash/mailhash.go
@@ -0,0 +1,94 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"xinu.tv/email"
+
+	"github.com/golang/glog"
+)
+
+var (
+	saveFile = flag.String("save", "", "filename to store unread status.")
+	loadFile = flag.String("load", "", "filename to load unread status.")
+	maildir  = flag.String("maildir", "", "Maildir root")
+)
+
+type Status struct {
+	Hash   string `json:"hash"`
+	Path   string `json:"path,omitempthashy"`
+	Unread bool   `json:"unread,omitempty"`
+}
+
+type Messages []Status
+
+func (m *Messages) hashMail(path string, info os.FileInfo, err error) error {
+	if info.IsDir() {
+		return nil
+	}
+	r, err := os.Open(path)
+	if err != nil {
+		glog.Fatal(err)
+	}
+	headers := []string{"to", "from", "cc", "date", "subject"}
+	h, err := email.Hash(r, headers)
+	if err != nil {
+		glog.Errorln(path, err)
+		return nil
+	}
+	md := email.NewInfo(path)
+	//fmt.Printf("%x %s\n", h.Sum(nil), path)
+	*m = append(*m, Status{
+		Path:   path,
+		Hash:   fmt.Sprintf("%x", h.Sum(nil)),
+		Unread: !md.Seen,
+	})
+	return nil
+}
+
+func (m *Messages) SaveStatus(maildir, saveFile string) error {
+	if err := filepath.Walk(maildir, m.hashMail); err != nil {
+		return err
+	}
+
+	b, err := json.MarshalIndent(m, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	f, err := os.Create(saveFile)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	n, err := f.Write(b)
+	if err != nil {
+		return err
+	}
+	if n != len(b) {
+		return fmt.Errorf("Short write of save status: wrote %d of %d", n,
+			len(b))
+	}
+	return nil
+}
+
+func main() {
+	defer glog.Flush()
+	flag.Parse()
+	m := Messages{}
+
+	if *maildir == "" {
+		glog.Fatal("Must specify Maildir with -maildir")
+	}
+
+	if *saveFile != "" {
+		if err := m.SaveStatus(*maildir, *saveFile); err != nil {
+			glog.Fatal(err)
+		}
+	}
+}
diff --git a/hash.go b/hash.go
new file mode 100644
index 0000000..b91ed46
--- /dev/null
+++ b/hash.go
@@ -0,0 +1,38 @@
+package email
+
+import (
+	"crypto/sha1"
+	"hash"
+	"io"
+	"net/mail"
+	"os"
+	"sort"
+
+	"github.com/golang/glog"
+)
+
+// Hash will parse r as an email, and return a hash.Hash that has been applied
+// to the values of the specified headers.
+func Hash(r io.Reader, headers []string) (hash.Hash, error) {
+	// Add deterministic behavior regardless of the order the users specified.
+	sort.Strings(headers)
+	var name string
+	if f, ok := r.(*os.File); ok {
+		name = f.Name()
+	}
+
+	h := sha1.New()
+	msg, err := mail.ReadMessage(r)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, header := range headers {
+		v := msg.Header.Get(header)
+		if v == "" {
+			glog.V(2).Infoln(name, "Empty", header, "header")
+		}
+		io.WriteString(h, v)
+	}
+	return h, nil
+}