The first step of DMARC implementation is reporting mode so none of your email settings will change. Only once you are sure that all your authorised traffic is properly configured will you move to a reject policy that will block all unauthorized use of your domain. We help you get to DMARC reject with confidence so you do not need to worry about the impact on your email sending. 

Implementing DMARC will require you to setup SPF and DKIM for all your providers that you send from so it will actually increase the deliverability of your authorised emails.