ok, all patches applied.

same process that worked in 2005 but not in 2008

same servers

same setup

You can send email in 2008 except when you @attach_query_result_as_file =1

The sp_send_dbmail returns successfully

That about everything?

I'm reaching but maybe try @query_attachment_filename = NULL

Try @append_query_error = 1

Are there any retries setup?

CEWII