GmailAPI for sending mail


I am trying to create a GPT lets call it Test GPT. At the end I want it to send an email to the user with regards to the conversation.
I have manage to set up the gmail API in a way that the mail goes to the user from the user itself after OAuth authentication with the Gmail API. I want to change it in a way such that the mail goes from a standard email id like to this user. So in this case the user should not get the oauth authentication page as it is not required.
Any tips on how to do this.