We don’t have this for our hosted customers, mandrill munges links inside digests to achieve this feature.
Long term there are a few things I would like us to do
- Add ?digest_id=XYZ to all links in digest
- Add a tracking “gif” so we can tell you opened the digest (and report on it)
- Add a general tracking gif to every reply email that sets “read” on post when you open it, opt in.