Seems nobody is replying this so I'll try to answer:
What I would recommend due my experience and the help given by Joe053204-xrx to ANYONE that have my ISSUE:
1- Check e-mail account (using a mail client like thunderbird). Try to send and receive emails.
2- Make sure your printer is compatible with your server authentication mode (if not, go to step 6)
3- If your mail server is external of your business place, make sure your ISP isn't blocking port 25 (its a common conduct due to spam)
4- Check the printer's email settings on its web page. Make sure the printer is able to resolve the name or reach the IP of the mail server
5- Try to sniff the traffic between your printer and your mail server: You'll need to install Wireshark and listen in promiscuous mode. To see the entire communication perfectly without missing any packet I would recommend connect a RJ45 HUB between PC and the printer, or using a network tap, or use cisco's SPAN port, or use the PC with wireshark as Printer's gateway by sharing internet connection (ICS). (If you don't know what I'm saying ask your system administrator). If you don't do any of those Wireshark is able to capture traffic (doing arp spoof and so on...) but depending on your network infrastructure you'll probably be missing packets.
6- If your printer is not compatible with your mail server's auth mode you have to install a RELAY to face the server and make the proper authentication for the printer.