Problem is, not all e-newsletters sent are mobile-optimized, i.e. images take hours to load, fonts are too small to read, the body doesn't scale according to my phone's resolution. And while phones can render these emails just fine, I'm not particularly fond of having to resort to pinch-to-zoom out. I mean why do that when I can simply receive an email that automatically scales and fit according to screen size.
What about you? How would you make sure that your emails are mobile-friendly?