Mail armor in general is just bad.
Dwarves of any type seem to look ok in it.
I have a hard time finding anything good for Draenei.
Orcs and trolls are ok, but not great.
Male Tauren look like “fat guy in a little coat” to me, but Female Tauren don’t suck.
My takes would be:
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Any Dwarf
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Female Tauren
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Male Orc
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Female Orc
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Any Troll
Beyond that, the other races will be hit or miss. You might find a piece that looks good on one, but another piece looks terrible and you won’t get a full mog out of it.