Warning was definitely the correct reaction!
I got that mail too. But it was not the 1st time I received a mail
exactly with this content! The last time i got it was when I had freshly signed in on a friendship/partnership community made by greenpeace!
Mails like this are not reliable and NOT to be trusted at all! They intend to get access to real data from naive users especially in social networks, and these informations WILL be abused! Sad, but true.
Do not respond! Do not give away any important e-mail-addresses! And if you did so: Forget this e-mail-account and build up another one.
We don't need to be loved by spammers and trolls

Instead this is a good opportunity to say loud and clearly No Thanks!
Best wishes to everybody,
bluna