The tweet has now been retweeted more than 12,000 times, and has gone viral across the world.
The screenshot shows Parker openly explaining that she has chosen to take what is commonly referred to as a 'mental health day', and that she would return to work "hopefully... refreshed and back to 100%" in a few days time.
Parker make the rare decision to be completely open about taking a mental health day - and her bosses response was refreshingly positive.
"I just wanted to personally thank you for sending emails like this," reads the email from her company's CEO, Ben Congleton.
"Every time you do, I use it 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. You are an example to us all, and help cut through the stigma so we can all bring our whole selves to work."
The concept of a mental health day is certainly not a new phenomenon - many of us have taken one at one point or another. However, due to the overwhelming stigmatisation and misunderstanding of mental health issues, the explanation for the sick leave is often purposely hidden, or left unsaid.
People on Twitter were surprised and happy to see such a supportive and compassionate response from Parker's boss, and began to share their own stories about the negative responses they received when taking mental health days from work.
Parker has been responding to many of the people sharing their stories with her, and has also recommended mental health groups to those who have been open about struggling at work.
If you are living with mental illness or are having a rough time right now, remember you can always call the friendly folk at Lifeline on 13 11 14 (and they also have an online chat option, if you don't feel up to talking).