After a 15-year run as Apple’s CEO, Tim Cook has handed the reins to longtime insider John Ternus. It marks the end of an era for the world’s most valuable company, as Cook moves into the role of executive chairman. And reflecting back on his time at the helm of the $4.75 trillion tech giant, Cook shares one daily leadership habit that pushed him to strive for success. 

“For the past 15 years I’ve started just about every morning the same way,” Cook shared in a community letter speaking on his tenure as CEO. “I open my email and I read notes I received the day before from Apple’s users all over the world.”

Since 2011, Cook has led Apple through a global pandemic, supply-chain upheaval, and the rise of AI—and has read thousands of messages about the products all along the way. Apple’s new executive chairman said customers would “share little pieces” of their world—from close calls caught by Apple watches, to capturing memories on their iPhones, to how their work has been changed since the dawn of the Mac computer. 

Whether it be heartfelt stories or complaints about the products, Cook says he combed through the messages daily, and said it’s been an “honor and a privilege” to lead the company building transformative tech.

“In every one of those emails I feel the beating heart of our shared humanity. I feel a sense of deepening obligation to work harder and push further,” Cook continued. “But most of all, I feel a gratitude that I cannot put into words, that I somehow got to be the person on the other end of those emails.”

Cook reads messages at 4 a.m. and reads hundreds of emails daily

Before most people have woken up to start their workdays, Cook has already been reading customer comments online. The former CEO gets up right before 4 a.m. every day, combs through hundreds of customer feedback to emails to get a sense of what users are experiencing.

“I rise a bit before four, I like to take the first hour and go through user comments and things like that, and sort of focus on the external people that are so important to us,” Cook told Axios in a 2018 interview. 

Then after a one hour workout to manage his stress, Cook dives right back into what Apple buyers have to say. He begins his 5 a.m. ritual of 15 years: reading “the majority of” the 700 to 800 emails that hit his inbox everyday. While many CEOs would delegate their flooded inboxes to their assistants, Cook said that “It keeps my hands on the pulse of what customers are feeling and thinking and doing.”

Cook is one of many emails who have embedded emailing into their daily routine—while others have eliminated the burden altogether. 

CEOs are split on how to handle emails

Just like Cook, billionaire Mark Cuban religiously checks his inbox—and his email is even available to the public. 

Rather than sit through hours-long meetings, he prefers to sift through hundreds of messages; he starts his day checking his morning emails around coffee, showering, and taking his daughter to school. And just like the former Apple CEO, he gets in a workout session before getting back to his inbox. Having an assistant handle his messages would only “slow things down.”

“I receive around 700 emails a day and use three phones (two Android and one iPhone) to manage everything,” Cuban wrote to Business Insider in 2025—ironically, over email. “I’d rather get 700 to 1,000 emails than sit in long, boring meetings.”

Other business leaders are adamant on emailing around the clock—even if it bleeds into the weekend. Uber CEO Dara Khosrowshahi revamped the company’s work culture when he stepped into the role in 2017, quickly implementing new ways to turn things around. One such change included emailing back whenever the need arises. If employees are “not performing” well in the “really demanding” environment, then Khosrowshahi said they’ll be shown the door. 

“Part of working hard is sending emails to the team on a Saturday,” the CEO of the $155.7 billion ride-hailing giant said on the Diary of a CEO podcast earlier this year. “And if I don’t get a response on Saturday, sending them an email on Sunday with a question mark. What’s going on?”

Brian Chesky, the cofounder and CEO of Airbnb, prefers to unplug. He runs the company on his own hours, doing away with morning meetings before 10 a.m., and rarely touching his inbox. Instead of shooting out emails, Chesky said he opts to call and text: “Don’t apologize for how you want to run your company.”

“[Emailing] was the thing about my job that I hated the most before the pandemic,” Chesky told The Wall Street Journal last year.

This story was originally featured on Fortune.com