It does not matter who and why you are sending a document. Always write the back story. “As per our discussion over the phone”. “Hi, this is Faisal; we met at Khan’s new year Party”. “Hi Arsalan, as we discussed in person, I am attaching my report on the number of hours you spent on the phone”. “Hello Jimmy, I hope this email finds you well. This is Faisal; we discussed a few opportunities available in your organizing while having a Turkish bath in Matera”. You get the picture.