Source: https://www.linkedin.com/pulse/how-configure-dkim-exchange-2019-simple-way-seyed-abdollahi Installation In Exchange Online DKIM is a built-in service, but on an on-prem Exchange 2019 deployment we need a 3rd party application to add this functionality to our Exchange infrastructure. In this guide we use Stefan Profanter's excellent dkim-exchange application for this purpose, which is available here: https://github.com/Pro/dkim-exchange/releases/latest After installing the program, we open Configuration.DkimSigner.exe and click on the "Install" button, or download the installer straight from https://codeload.github.com/Pro/dkim-exchange/legacy.zip/v*** Configuration After installation finished, open the configurator. C:\Program Files\Exchange DkimSigner\Configuration.DkimSigner.exe Click on the "Configure" button and move the DkimSigner agent to the very bottom of the list. Under the DKIM settings tab select relaxed canonicalization as Exchange t...