First off congratulations! Any email from anyone liking your music is a great feeling and motivational boost.
With my experience A&R agents will contact you via email, phone, facebook, or whatever platform you are on to reach you. It has happened to a few of my close friends in the industry and now they have specific contracts for licensing and selling their music in the Industry, Although don't jump the gun so soon. Sites like Reverb Nation main purpose is to promote music on THEIR website. Find out what they are looking for from you before you sign any documents. They want to take your music to labels? Ask if a label representative could contact you for more information on what they want with your music. Don't quote me on this but labels usually care more about the profit they could get from your music rather then you receiving any profit either financially or recognition wise.
My main advice that I got from the Industry is if you want to grow your career, sacrifice your music for a chance to have connections with A&R's and other music lobbyists. Make sure your music is protected by signing up with a performing rights publishing company. Regardless you have intellectual copyrights on your music as long as you have it on your DAW.
Hope this helps. You could contact me with any other questions you have.
One thing I learned from the industry is that no one is "Self-Made"... Everyone has gotten help from Everyone in the industry... so pass it on!
Jason Kellner
Film Composer/Orchestrator/Arranger/Music Copyist/Pianist
Montreal, Canada