I'm trying to set up iCloud Mail with my domain using Apple's instructions here: https://support.apple.com/en-us/HT212524
Dynadot's interface doesn't seem to like the format that any of these records are in. I think I have to create a subdomain, but I'm confused as to how.
Apple specifies a Type, Host, Value for each of 5 DNS records (2 MX, 2 TXT, 1 CNAME), but Dynadot DNS record entries only have 2 fields: "Record Type" and "IP Address or Target Host".
You can omit the "Host @" entries that Apple specifies for MX and TXT records. Simply put the Value that Apple specifies in the "IP Address or Target Host" field.
For the DKIM entry, you need to specify a CNAME record for a subdomain, as outlined here: https://www.dynadot.com/community/help/question/enter-DKIM
I created a subdomain CNAME record, put the Host that Apple specified in the "Subdomain" field, and put the Value that Apple specified in the "IP Address or Target Host" field. Worked like a charm!
Don't forget to set the Time to Live (TTL) to 1 hour, per Apple's specification. (I don't know how important this is, but Apple does specify the TTL, so...)