Nos es?

I just came across this sentence in an email- "Nos es muy grato saber que..." I understand what he's saying but the grammar seems completely at odds with what I know of Spanish. Nos is a pronoun, so why is he using is as "we"? Shouldn't he be using "nosotros"? Why is "es" used, when he seems to be referring to "we"? Shouldn't it be "somos"? And wouldn't "estar" be more appropriate than "ser" since he's referring to a temporary emotional state? Or is this just one of those sayings that can't be explained grammatically and I will just have to get used to?

Hola Wendigo. Bienvenido al foro. The grammar actually does make sense. "Grato" is an adjective that means "pleasing." A literal translation would be "to us it is very pleasing to know that...." Do you see now why the indirect object "nos" is used instead of the subject form "nosotros"? The subject of the sentence is not we/nosotros but rather the impersonal it (understood from the verb es--it is).