You could also use an open DNS server not attributed to an ISP, DNS was the primary issue here from what the fault was, not SMTP.
The fact you could not use SMTP.gmail.com but could use it's IP address also indicates the issue was the DNS settings from the beginning.
Quickest resolution almost certainly would have been to use your gateway address as a DNS server (192.168.1.1) and also Google's Open DNS server which is 8.8.8.8. Neither of which relies on your ISP directly as the router will pick up the correct DNS settings and forward the machine requests,
And this way you don't have to worry about DHCP messing up your print capability down the line.