"I use (your email) as a reminder of the importance of using sick days for mental health - I can't believe this is not standard practice at all organisations," Congleton wrote.
"You are an example to us all, and help cut through the stigma so we can all bring our whole selves to work."
Parker went on to share screengrabs of the email exchange on Twitter. The tweet, posted on June 30, has since been retweeted more than 11,000 times.
Congleton was praised by some Twitter users for the refreshing response.
The CEO took the email exchange a step further, writing about mental health in the workplace on Medium.
"Even in the safest environment it is still uncommon to be direct with your co-workers about mental health issues. I wanted to call this out and express gratitude for Madalyn's bravery in helping us normalise mental health as a normal health issue," he wrote.
"As executives, we lead organisations made up of people who've come together to make an impact. Our job is to empower and motivate our teams to maximise the impact of our organisation for our customers, our employees, our shareholders, and the world."
