Hm... seems like Seam cannot find a component named "inboxEnvelopeSearch"... just a small idea: Is the InboxEnvelopeSearchBean annotated with @Name("inboxEnvelopeSearch")? Maybe a typo somewhere?
A couple of things
1. Make sure your web page references the correct Seam Named Component.
2. Make sure your Scope is appropriate.
I've found that the exception you get always points back to one of these two things. There could be others, but this is what I've seen.
Most likely bfo81 is correct and it's a component naming issue.