That's not really the right approach.
The problem is simply the default top margin on the p element. Set the top margin on all your p elements to zero (using inline-css for emails). The same would apply to h(n) tags also as they also have default top (and bottom) margins.
Your display:inherit worked because it turned the p element into a display:table-cell element and table-cells cannot have margins and thus was ignored. However the likelihood of email clients understanding that rule would be less than the margin rule. It also means that the element becomes a table-cell and you get all the behaviours that go with it which may trip you up later.