With this tool, your IIS SMTP Service and Exchange Server will be enabled to add DomainKeys/DKIM signature to outgoing emails from specified domain(s), which verify the DNS domain of an email sender and the message integrity, and in turn preventing the emails from your domain from being flagged as spam or junk mail by email servers which have Domainkeys/DKIM implemented (such as Hotmail, Yahoo mail and Gmail).
See Also
Setup DomainKeys/DKIM
Deploy Public Key in DNS server
Test DomainKeys/DKIM signature
Troubleshooting
Using Selector
Using Sender Rule
Server Core and Installer Command Arguments
Appendix - Set up SPF record in DNS server
Appendix - Set up DMARC record
Appendix - DKIM/SPF/DMARC Inbound Authentication in Exchange Server
Appendix - Use DkimPowerShell Module in PowerShell
Online
DKIM in IIS SMTP Service - Tutorial
DKIM in Exchange Server 2000/2003 - Tutorial
DKIM in Exchange Server 2007/2010/2013/2016/2019 - Tutorial
Bulk Email Sender Guidelines