I got it but some in my FS said that they didn't. But I have seen Elvenar emails show up in my spam folder, so if you didn't receive one, I would check there.
Also, if you go to Settings, there is an option to verify your email address. It's possible that some players never did this and consequently never received their 50 free diamonds, and may never have been signed up to receive the Elvenar newsletter.
They don't bug you often, so I would advise anyone who doesn't receive these emails to do this so they don't miss out on these occasional offers.