Hoping to get some advice here on how much more investigation or testing I need to do. I read the help documentation here: https://help.salesforce.com/s/articleView?id=000388992&type=1 and I think my org's email deliverability will be unaffected. We don't have any relays or domain filters set up, and I have an active DKIM key. We also don't have any IP restrictions. Is it still necessary to test deliverability, and how do I go about doing that?
Also, the below is key to get to your email admin prior to migration to hyperforce.
For Emails being filtered by anti-spoofing after hyperforce migration for your reference :
https://help.salesforce.com/s/articleView?id=000396202&type=1
Add SPF record _spf.salesforce.com in your domain.
To add SPF record in your org please find below help article :
https://help.salesforce.com/s/articleView?id=000382664&type=1