We have an Exchange 2010 Hybrid w/ O365 setup for mailflow for @Ourdomain.com.
We use a cloud e-mail gateway that processes e-mail coming in and going out as well.
But we are looking to add a listserv server on-prem called "Sympa".
We'd be looking at using listserv.ourdomain.com as a subdomain for the e-mail address for our SYmpa listserv.
Would we need to add a new MX record or just an A record?