sudo apt-get install opendkim opendkim-tools

# must enter the customer's host name
opendkim-genkey -t -s default -d customer.domain.edu

# add pcr360 as a subdomain
vi default.txt
# edit this line to, then save and close
default._domainkey.pcr360

#copy the private key
sudo mkdir /etc/opendkim
sudo cp default.private /etc/opendkim

#edit the DKIM configs
vi /etc/opendkim.conf
# uncomment and edit the following lines
# must enter the customer's host name
Domain                  customer.domain.edu
KeyFile                 /etc/opendkim/default.private
Selector                default

vi /etc/default/opendkim
# comment out the current socket line and add this
SOCKET=inet:8891@127.0.0.1

# start the dkim service
sudo service opendkim start

# edit the sendmail config
vi /etc/mail/sendmail.mc
# add the end of the file
INPUT_MAIL_FILTER(`opendkim', `S=inet:8891@127.0.0.1')dnl

# become root
sudo su
#  rebuild the sendmail config
m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

sudo service sendmail restart