Solution:

$ torsocks pacman -S swaks perl-net-ssleay

$ nano notes.txt
$ torsocks swaks --server tmg3kli67jlbcduh.onion --to [email protected] --from [email protected] --helo "returnaddress.onion" --tls --body notes.txt

encrypt notes.txt with my public key for extra points.

Status: Just tested it, working.