A few points:
1) I agree with others that there isn't a technical solution to this.
2) It should be pointed out that most mobile email clients top post and do not provide an easy option to do otherwise. It is also the default for the Gmail BUI.
3) Top-posting is widely accepted and preferred in some communities and the same for bottom posting. Both have pros and cons and I found generally that it is not helpful to assert preference as fact.
4) In the groups that I admin, I advocate for what I call per thread consistency. The first reply sets the rule: if the first response is a bottom post, please continue that way, same for top posting. Because to me, the real mess only starts when someone top posts to a bottom posted reply or vice-versa.
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