Most of these are from qslworld and seem to be from totally random quite old qsos and nothing special. I think the intention is that you should join yourself and reply via their system. Replies sent as replies to the email probably never reach your qso partner. I just delete these now, but if you want to sign up to qslworld you are of course entitled to do so. eqsl operate a different system in that the system has a function to tell a qso partner that there are eqls waiting but the actual cards are not emailed.
73 Dave G3YMC
Dave Sergeant G3YMC