I found this problem a few days ago and a great friend recommended me this magical tool.
I needed test some email changes on a Magento 2 project, but my local SMTP stopped working for some reason, I tried to install some Magento 2 extensions to use my Gmail as SMTP but I was not lucky, several login problems made me look for another alternative.
I commented my problem to a friend and he recommended me this tool.
The tool in question is MailHog. It is just magic, after the installation you have a kind of "inbox" where you will see all the emails that you will send through PHP.
This is the guide to install it on MAC (tested): https://github.com/maijs/homebrew-mailhog
For Linux (not tested): https://gist.github.com/varghesejacob/68caf7aeee53305a1ffa#file-mailhog-bash-script