For all the coding brothers, here is a tip:
In Outlook and Yahoo in few browsers dosent allow us to use typical div based responsive layout. You got to do it in old fashioned table way but style it to give newer look.
You cannot use images from different domain that your email is considered spam.
You cannot use more than 150KB of total size of all images
There are more that needs to be handled for various aspects. But this should be good for starters.