When sending InfoPath Form in the body of the email, usually the formatting is gone out. The tables and Controls are not aligned properly; Form is embedded as an image.
1 – You can use only calculated fields in the InfoPath Form – funny thing but it is tried and tested.
2 – Use Nintex or SharePoint Designer to set email contents for Users.
I just used InfoPath 2013 + Outlook 2016 and SharePoint Online, it works and formatting is good if you use 1 table and make sections to hide form fields, key is to use 1 table and embed your solution in it.