Domain Key not showing up in DNS query
Solution 1:
Whether or not you added them to your registrar's DNS servers... I cannot say. What I can say, is that the records are not publicly resolvable. Are you sure you didn't define the records as SRV or A records? If you're 100% sure you added them properly... it's time to call Namecheap... and talk to them. Maybe they have issues hosting TXT records.
Solution 2:
As indicated in the edit to the question, changing from e.g. default._domainkey.example.com to default._domainkey resolves the problem.
It looks like Namecheap appends the domain name, so default._domainkey.example.com becomes default._domainkey.example.com.example.com.
To test this theory I did a DNS lookup:
nslookup -q=TXT default._domainkey.example.com.example.com
Sure enough, there was the TXT record. A quick check of TXT records on MXToolBox confirmed it as well.
Solution 3:
[SOLVED] Basically, I had the same issue. Added DKIM (CNAME) and SPF (TXT) records in Namecheap for Mailchimp integration but got this message from Mailchimp.
We tried to verify your DNS changes and did not detect the right values
The issue is Mailchimp asks for this string to be added in the host field.
k1._domainkey.domainname.com
But as someone suggested above, in Namecheap you don't need to include the domainname. In my case for mailchimp, just k1._domainkey was enough. I double-checked with the Namecheap guys. They confirmed it and pointed me to this guide.
https://www.namecheap.com/support/knowledgebase/article.aspx/9845/2208/how-to-connect-a-domain-to-mailchimp
Just one more trick. Mailchimp continued to show me the error even after DKIM check was right. (Tool here: https://toolbox.googleapps.com/apps/dig/#CNAME/k1._domainkey.dasubhashitam.com)
What I did was remove the verification in mailchimp and do it again as suggested in the guide. Voila! Things worked. And I wasted two days on this.
Hope it helps somebody.
Solution 4:
What solved for me was NOT using the domain name as selector name. Never have a DNS entry that's like
website._domainkey.website.com.
using
def._domainkey.website.com.
worked for me!