Most Unix/Linux tools, like grep, need a plain text file as input. Windows doc format isn't plain text.
You could try using grep's --binary-files=text
option, but this could output binary code to your terminal which in turn can ruin your terminal session:
egrep --binary-files=text "Email |email |@" /opt/data/ca/aa.doc
Otherwise you need to convert the doc to plain text and use that as input.