In The Phrase'your Help Is Appreciated' Is 'is' The Main Verb And'appreciated' An Adjective
To be sure, "appreciated" doesn't modify the verb (since it is not intended to indicate that the action is performed in an appreciative manner, or in a manner which is appreciated); rather, it complements the verb.
But to prove that things are never as simple as they seem, this construction could be analysed in different ways.
You could say that "appreciated" is a passive adverbial. Or you could say that the whole sentence is a straightforward passive, and that "appreciated" is simply the past participle of "appreciate":
Someone eats the cake. (Active)
-> The cake is eaten (by someone). (Passive)
We appreciate your help. (Active)
-> Your help is appreciated (by us). (Passive)
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