External requests from letsencrypt need to be proxied to the port specified in the mapping
docker run \
-e CONSUL_CONNECT=localhost:8500 \
-e FQDN=example.com \
-e EMAIL=admin@example.com \
-v /home/user/ssl:/certificates \
-v /home/user/letsencrypt:/etc/letsencrypt \
-p 127.0.0.1:9999:80
-d \
phylor/letsencrypt-consul