Some back of the envelope calculations.
20M “opt-in” leads a month is roughly 650,000 leads a day.
650,000 leads a day is roughly 27,000 leads an hour.
27,000 leads an hour is 450 leads a minute.
450 leads per minute is one lead every 133 milliseconds.
The total population of the US is roughly 300,000,000 people.
20M leads a month is every American with an email account in the course of one year.
Does 20M leads a month really sound realistic?