There’s a small (but probably good to fix) bug in DKIM setup that produces invalid DKIM records.
Specifically, a record is created along the lines of:
k=rsa; v=DKIM1; o=-; p=…
If the v= tag is present it MUST be the first entry in the record, per the DKIM RFC. Interworx should make sure that the v= is first.
Aside from that, but not technically an error, is the o= value isn’t defined so it’s unclear why interworx adds it. The RFC explicitly states clients must be okay with extra key/value pairs, so it shouldn’t affect operability. But it’s odd that it’s there.
Also, it creates a bare “_domainkey.domain.com” record with just “v=DKIM1; o=-;” as the contents. I am not entirely sure on the spec to know if this record makes sense, but it doesn’t seem to from what I know.