> You don't think lady in 'mail-lady' refers to woman?

It can either refer to their sex or their gender.

> Rude. I never would. But if I did it would be redundant after calling her a woman. What do you mean?

If we refer to sex, a woman/lady is someone with a vagina. So yes, if you call someone a mail lady, you literally are describing her as a mail carrier with a vagina.

> But maybe I'm trying to help my brother find a partner so I do want to point out available women, and that does imply people with vaginas. Again, so, and what do you think would be a more efficient way to do this?

In that case, you might also talk about "the cute ginger mail lady with blue eyes" (or whatever your brother likes). But in most situations, that would be quite inappropriate.