Hey Drew, thanks for that.
I should have mentioned in my first post that there had been no propagation after 96 hours.
The GoDaddy tech support have resolved this issue now.
The root cause is that what entries you add into the GoDaddy DNS management portal, and which look like the DNS records you would expect them to be, are in fact amended by the GoDaddy 'back end' systems before being converted to DNS records.
For example, in my case, I entered a TXT record as follows into the GoDaddy portal.
TXT mailjet._domainkey.<mydomain> k=rsa; <SHA256 encryption key>
What appears to happen is that the GoDaddy portal accepts this, displays it back to you but when being added to to the GoDaddy nameservers it is added as:
TXT mailjet._domainkey.<mydomain>.<mydomain> k=rsa; <SHA256 encryption key>
In other words, <mydomain> is being added for a second time to the TXT name field.
My issue wasn't helped by the fact that the instructions from my mail provider mailjet.com at: https://app.mailjet.com/docs/godaddy-setup-spf-dkim-record would seem to be incorrect. So in fact the correct method on the GoDaddy portal is to input the following:
TXT mailjet._domainkey k=rsa; <SHA256 encryption key>
and let GoDaddy portal add on the <mydomain>.
By comparison, the DNS record portal at IBM's softlayer Cloud portal expects the <mydomain> to be included when the record is added. Their portal does not append the <mydomain> name.
Clearly, there is a lack of standardisation here.
I have contacted Mailjet to ask them to correct their instructions, and I'd like a big shout out to Arminder at GoDaddy tech support who spent couple of hours with me diagnosing and fixing this.
