First, I had named the droplet “main” (since it was, you know, the main server), but this really should be a Fully Qualified Domain Name (FQDN) instead. So I renamed the droplet to main.bhconsulting.ca and restarted sendmail. However looking at the mail logs I saw lots of:
unable to qualify my own domain name (main) — using short name
Since it was still using “main” as the server name. Thanks to help from this thread I modified the /etc/hosts file from:
127.0.1.1 main main
127.0.0.1 localhost.localdomain localhost main.bhconsulting.ca
127.0.1.1 main.bhconsulting.ca main
voila, fast sendmail.