SDR = Sender Domain Reputation A big part of the ESA's efficacy was its IP reputation engine (SBRS), with the move to cloud based email, IP because less useful because everyone, good actors and bad actors is using the same set of IPs from Microsoft or Gmail...
SDR was developed to deal with that. They also include things like domain age in that calculation.
Sender domain verification is different. This is about verifying that all of the various DNS entries exist for a domain.
You do want to enable SDR, set it to reject "untrusted", and you may want to create a content filter with an age limit for very new domains, and quarantine that mail. (e.g. <29 days.)
Note that if the age is over 30, SDR returns 30... so even old domains show up as "30 days old" which caused me quite an issue when then first switched to that.
