With that said – this post by the guys over at STYLECampaign will reduce some of your time if you are sending a decent chunk of emails to people who read your email on an iphone.
Some of the things looked at include:
1. understanding zoom and sizing
2. Customising the look and feel of the email by device
3. font scaling
There are 2 parts – read them both in full here and here.
I can see the use of device specific templates being something that will be needed more and more in the future. The trick is going to be to do so in a cost effective way.