My company sends out emails through our own server. (We don't hire an email service provider.) I've written (in most cases, copied and pasted) some industry standard coding for responsive emails and then tested them through our software, Sendblaster. However, the responsive columns do not work.

In between campaigns (which is never), I've tried to squeeze in some testing with other email sending software programs. I found one that works, GroupMail, but I'm not sure how much I like the interface and tracking options, pricing, etc.

Can anybody recommend email software programs that have been proven to work with responsive columns?