DKIM signature

dear all,

I'v got a few mail in eml format. I am using opendkim on ubuntu linux to verify the eml. The public key is in pem format. The syntax I use is

opendkim-testmsg -v -d aruba.it -s a1 -k publickey.pem < namefile.eml

But the answer is reosurce unavailable

Is available any other tool? I prefer not online

thanks in advance