targeting hotspot users

Basically I started a SMTP server for my own needs, as I couldn't use
my own ISP's smtp server when using WiFi hotspots in hotels, airports
etc.

I've now branded my smtp server as the SMTP-King and would be
interested in advertising it to people who would like to use their mail
client like outlook whilst on wifi hotspots (for a cover charge)... so
my question is what's the best way to reach such people and let them
know (and if you like market it)? Someone must have a good idea out
there! I'm stumped. Google ads is one way, but tests show it to be not
that good for this purpose, but is there a hotspot company I could tie
up with, or a magazine that would be ideal? any new thoughts?

I won't mention the web site URL in this email, so as not to be seen as
using this as an advert, and maintain good netiquette!

Thanks,
Doug.