Customizing user welcome email

Dear Team!
I use a user registration form with contact form 7 and set a welcome E-Mail which fires after registration. In this email I would like to integrate the information regarding the new username, the password and the link for login (which is provided at the moment by the wp new user notification mail). So I want to avoid that the new user gets two mails (from contact form 7 and the wp notification mail).
Thank you for your support, Stefan

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