Implement Mail service.

service/mail/interface.go

Index: service/mail/interface.go
diff --git a/service/mail/interface.go b/service/mail/interface.go
new file mode 100644
index 0000000000000000000000000000000000000000..813797c27e2e9a625b9b9adf15fc39d46f88844f
--- /dev/null
+++ b/service/mail/interface.go
@@ -0,0 +1,16 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package mail
+
+// Interface is the interface for all of the mail methods.
+//
+// These replicate the methods found here:
+// https://godoc.org/google.golang.org/appengine/mail
+type Interface interface {
+	Send(msg *Message) error
+	SendToAdmins(msg *Message) error
+
+	Testable() Testable
+}