Letter from Post Office

[alsmom360]

I think you should just ignore it completely.

Is this the norm for people to receive letters?     Is this the infamous LL i've read about?
I've never had one, but you would think they would
send it certified so that they would make sure it was received.
Has anyone had a follow up to the first one delivered and if 
so what did it say?
I'm glad I read about it here, or I might have to freak if
something like that popped up in my box!  I'm assuming now it's
nothing to worry about.