Hi,
API users and resellers are a real business. You sure can clean 5k emails in one go but 20k emails verification worth of credits is required to get started as a reseller. Please do that first if you really want to resell.
The details you will receive is very detailed and this will be in the Excel csv file you will receive after verification is completed, the doc asks you to fill in a parameter where you enter your email address to receive the full verification details and those details will sure include mx records vs no mx records, dns lacking vs dns available etc. In fact you will receive at least two files. One with only clean list, the other with all verification output details for each email address you verified via API.