Emails with "Unsubscribe" box at the top

Hi All (and especially HDF5 Forum List Manager(s))

There appear to be several cases of emails arriving to HDF5 Forum list that look like the one below.

When someone 'replies' to an email that looks like this (well, when I did anyways), it winds up generating an unsubscribe request to the list.

Something seems amiss here and I can't tell if its really my own local IT issue that is the cause, somone elses or the hdf-forum list itself.

But, it seems like a problem someone, somewhere might have the advice on how to 'fix'