We have two different systems, that send out email using our domain, @mathieu.company .com.
Other one of these systems is our Exchange Online, that we use to normal company email. Other system is our infomail system, which send out emails by itself, so there is relay connection to Exchange Online. Infomail is totally separate and different system from Exchange Online and this system's IP is added to our SPF TXT record to allow to send emails using our domain, @mathieu.company .com.
If we enable DKIM in Exchange Online, so that all email sent out from Exchange Online would have encrypted DKIM singature, but we do not enable DKIM signing to our infomail system, would all emails sent out from infomail system get denied/quarantined etc.?
Basically, is DKIM sort of global setting? If we enable it to Exchange Online, will emails sent out from infomail system also get checked agains DKIM?