The sportswear giant admitted its choice of words had been "insensitive" and said it was "incredibly sorry" for sending the document.
The company "deeply" apologized for what it said was a mistake.
Instead the company congratulated those who "survived" the Boston Marathon and apparently forgot about the 2013 tragedy at the race. She placed 24th for women in the 2017 Boston Marathon.
In a statement to TIME, a spokesman for Adidas apologized for the email.
The first woman to officially run the Boston Marathon has marked five decades since her achievement by running it again - at the age of 70.
In 2016, a movie titled Patriots Day, starring Mark Wahlberg and Kevin Bacon, was released.
"Adidas, you may want to rethink the subject line", wrote Mike Denison. Kendall Jenner's Pepsi scandal was the most popular among them.
Switzer won the New York Marathon in 1974 and continued to run Boston until 1976 before providing TV commentary for the next 37 years.
A poorly worded email has people on social media wondering when Adidas may issue an apology.
The Boston Marathon was the target of a terrorist attack back in 2013 that ultimately killed six people and injured hundreds of others.
"Adidas is going to have to fire whoever was in charge of writing this e-mail", one person wrote on Twitter. "We can make it happen through running".
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