Email attachment sent without permission or action

I received and email from one user yesterday which had an attachment (zip file). Later that evening I responded to a second unrelated email from a different contact in a different company and discovered that the zip file from the first email had somehow been attached to the response. This was flagged to me this evening when the second contact was asking me why I sent him the zip file.

This is seriously alarming as I do not know any way to attach a file to a email response on the iPad. The iPad I am using is a 128GB IPad Air.

This behavior will force me to stop using my exchange account on the iPad.