EmailJs expects a specific format. Try updating the key value pairs as follows:

to_email: email, 
from_name: 'Email Confirmation',
to_name: email.split('@')[0],  
message: `Please confirm your email by clicking the link: ${confirmationLink}`

change "to" to "to_email" and set "reply_to" to "to_name".

If this doesnt work, make sure your environment variables are properly set in docker and also consider adding logging to help debug errors.