The billionaire entrepreneur spends all day dipping in and out of his inbox—he even likes sifting through hundreds of emails a day, more than in-person meetings. 

“I receive around 700 emails a day and use three phones (two Android and one iPhone) to manage everything,” Cuban wrote to Business Insider, ironically over email. I’d rather get 700 to 1,000 emails than sit in long, boring meetings.”

Cuban told Business Insider that his day is “boring,” emailing in spurts around his morning decaf coffee and cookie, shower, and taking his daughter to school. He then gets in a workout session at Life Time Fitness before taking a second shower and returning to his inbox.

“I read and respond to emails. I work out. I read and respond to emails. I do a couple Zooms. Then I read and respond to emails. Then I eat dinner. Then I read and respond to emails.”

People may expect the iconic ex-Shark Tank investor to have an assistant run his email for him—but he’s adamant on doing it all himself, reasoning it’ll only “slow things down.” But he isn’t simply hacking away at unread emails with a strategy; Cuban has forged a calculated plan throughout the years to whittle down his messages efficiently. 

Using his favorite communication method, Fortune reached out to Cuban for comment via email. 

Mark Cuban’s productive email set-up: AI replies, and no days off

Cuban is an email lover, preferring the line of communication over Slack, texting, and calling. The serial investor told Business Insider it’s his favorite because emails can be searched decades later, as he has messages going back to the 1990s. He began sending out emails in the 1980s on CompuServe—the company that acquired Cuban’s MicroSolutions business for $6 billion—and still has a bunch of those folders with his former employees’ addresses. 

The 66-year-old businessman also sees the communications format as more productive. Handling business dealings, employee communications, and press requests “asynchronously” from all across the country and world. Emailing makes it easier to get things done on his timeline—plus, everyone has it in their back pocket.

“There’s also really no limit to the type or format of the content. I can include it in emails or attach whatever,” Cuban wrote. “Everyone has email. In 2025, I don’t know anyone who doesn’t…It’s fast. Particularly now, with Google’s auto replies.”

But there’s also a method to Cuban’s emailing madness, other than simply checking his inbox and responding to emails repeatedly throughout the day. 

For 10% to 20% of his emails, Cuban said he uses one of Gmail’s recommended responses, saving him some time and brain power. He allows AI to write his autoreplies occasionally, or uses the tool as a “typing hack” to save time in writing long responses, but noted that he’s “typically going to add some flavor somewhere.” 

He also uses folders to keep his inbox organized, as he’s had too many emails over the years. 

While Cuban said that he never wants to hit inbox zero because he purposefully keeps some emails unread as reminders, he aims to keep these to under 20 messages. On occasion, he can get that number down to under 10.

It’s an ambitious goal that requires a constant clean-up of his inbox and means Cuban almost never takes a break from his email—only stepping away for a day or longer during an “extraordinary event,” like attending special events for his family. 

“I have a hard time disconnecting,” Cuban wrote. “It’s faster to just get it out of the way.”