“Intersex” is still very popular, although by no means exclusively used, in the USA, which is linguistically backwards in other ways too.
I’ve noticed the term “child porn” for example is still very much in use over there, by statutory agencies as much as uninformed individuals, while here you see it less and less. People over here, certainly those whose work is in any way connected with fighting CSA/CSE, tend to use more accurate terms like “images of child abuse”, as do others who are aware and care about the issue.
Likewise “intersex” vs “people with DSDs”. As Helleofabore says, there are MNers who themselves have DSDs and have expressed their feelings on the matter, and also there are those with DSDs that many of us follow on Twitter: we listen to the people personally affected by the issue who have spoken directly to us.
And just think about it. “Intersex” is an outdated, inaccurate term. No one is actually between the sexes. The human body develops along one of two pathways, in terms of reproductive function: whatever variations or disorders may manifest in that development, each human body - each person - still falls into one of the two categories, develops along the pathway of producing large gametes or small ones. Even if that body, that person, ultimately produces neither.
But anyway. There is no reason at all to use any of this language about people who don’t have DSDs, which is the vast majority of the population - no reason except the furtherance of a quasi-religious, highly controversial and noticeably authoritarian ideology which has been imposed by stealth on our supposedly reason-based, democratic societies.
Which is the point that needs to be made to the very confused person who sent that email to the OP.