Your comments

Just tried ajenti-v-mail off a clean Ubuntu install 14.04 LTS and received the same error message --

2015-07-14 06:14:44 H=( [::1] F=<> rejected RCPT <>: relay not permitted

Wish I could've waited for a response but my clients were being picky, had to move back to ZPanel/Sentora. The reason I love Ajenti is because it's Node-friendly. I'd still appreciate any possible suggestions on a fix, for future reference.
Update : So I tried running the following exim check out of curiosity,
exim -bt foo@mydomain.tld
and received the following output,
foo@mydomain.tld is undeliverable: Unrouteable address
Got it working! Thanks for the help,

@Anyone having the same problem,
  1. chown www-data:www-data (group/user) to your website directory.
  2. Install policycoreutils-python from epel's repo.
  3. Run,

cat /var/log/audit/audit.log | grep nginx | grep denied | audit2allow -M mynginx
semodule -i mynginx.pp
Chown'd the www-data group/user to my website directory, now getting :
-time- [crit] 7080#0: * connect() to failed (13: Permission denied) while connecting to upstream, client:, server: n, request: "GET / HTTP/1.1", upstream: "", host: ""

For whatever reason ( may have been the chmod ), my error logs are populated with messages. The recurring theme seems to be,
-time- [crit] 6741#0: * connect() to failed (13: Permission denied) while connecting to upstream, client: -client ip-, server: $
No luck, if it's not too much trouble, could you try setting up a node site using the latest version of Keystone on Ajenti-V w/ NGINX and report your results? I don't know why port 80 isn't proxying to 3000, it makes absolutely no sense.
I'm starting to believe it may be a problem with KeystoneJS. I'll look more into this tomorrow and post my results.
Sorry for the late reply, I was at work. As for restarting NGINX, I've tried this several times, I've restarted the server, etc. etc etc.

The issue honestly doesn't make sense to me, as the NGINX configuration should work.