I would say 'No, this is yesterday's' or 'No, this is yesterday's mail' or 'No, this is from yesterday' and it could even be 'No, this is from yesterday's mail collection'. I wouldn't say 'this is from yesterday's' because this is missing a noun - when you add 's to yesterday it becomes a possessive adjective so it needs to have a noun to possess and describe. in the first case 'this is yesterday's' this is no problem because your noun is whatever 'this' refers to. when you add a from in 'this is from yesterday's', from breaks up the clause and 'this' no longer refers to the object too, so you need to specify an object to complete the phrase, like I did when I said "this is from yesterday's mail collection" hope this helps!