SMTP: response code "235" but got code "535"

This is probably more a PHP error, but I came across it in the context of bookstacks. When configuring the .env file to connect to a mail server, and testing the email, you might get this error: 

 unexpected response code "235" but got code "535", with message "535 Error: authentication failed".". Authenticator "PLAIN" returned "Expected response code "235" but got code "535 

 The problem goes away when you put the password in quotes a such: 

   

   

 MAIL_PASSWORD="thIsIsYour873#password"