Screen reader compatibility for emails

Constant Contact does not comply with the Americans with Disabilities Act Accessibility standards because it does not allow the sender to designate certain text as headings.   I have heard tale that there is some way to do this using html code - but I have not been able to easily find it.  Also if I were going to edit the code for things as simple as headings what am I paying for.   Please advise if there is any way to designate headings for accessibility users currently and if there is any plan to make this feature user friendly in the interface.