How to send a PGP-encrypted email from the CLI?

Hello,

I'm trying to send an encrypted email via a cron job. I can't get it to
work. For instance, I tried the following command, but it opens up mutt
for an interactive session:

echo "encrypted msg" | gpg -e --armor -f <pub_key> | \ 
    mutt -s "PGP test" \
         -e "my_hdr MIME-Version: 1.0" \
         -e "my_hdr Content-Type: application/pgp-encrypted" \
         -e "my_hdr Content-Disposition: inline" [email protected]

Also tried the following:

echo "encrypted msg" | gpg -e --armor -f <pub_key> | \ 
    mutt -s "PGP test" \
         -e "my_hdr MIME-Version: 1.0" \
         -e "my_hdr Content-Type: multipart/encrypted; protocol='application/pgp-encrypted'" \
         -e "my_hdr Content-Disposition: inline" [email protected]

And I get the error: Error in command line:
protocol=application/pgp-encrypted: unknown command

Is there a way to accomplish this (ideally, without creating temporary
files for the encrypted part)?

-- 
W. D. Sadeep 
PGP: 103BF9E3E750BF7E