Ensure you are not using a reply address from @fusionauth.io; if you are this will fail our DMARC policy.
You don’t necessarily want to remove this reply address, but it should not be using our email domain. Instead it should be an address that belongs to your organization, such as email@example.com. (Or, even better: firstname.lastname@example.org--I hate when I get an email I can't reply to, myself.)
Each email template also has the option to override that default value with a different value. So you may also want to audit each email template to ensure if it is using a different From address, it is also owned by your domain.