While I have never rec'd any 50$ e-mails, I have rec'd a 5$-one a couple of times, and, of course, a lot of 1$-ones.
I have responded to a lot of their offers as I find them valuable or needed-purchases anyways.
If I was running e-rewards, I would send more offers to those who respond positively to the value of offers which are available and to those who actually purchase more (i.e. follow through to the end with a transaction). Sooooo, if they think like me then you might possibly have an answer as to why some get more e-mails than others.
By the way, today I rec'd 3 offers. Nothing for a week and then 3 in row. Go figure.
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Got points ? Got smiles !