Cannot create CNAME with underscore
To setup a DKIM record, I need to create a CNAME record with this Host Name:
k2._domainkey
But it fails with this error:
Invalid hostname k2._domainkey
Removing the underscore will create a record, but it is required for a valid DKIM record.
How to get around this?
9 Replies
tlambert
Linode Staff
✓ Best Answer
@juans @vineethraj49
After an investigation from our Administrators a hotfix has been deployed for this issue. You should now be able to add a CNAME record with an underscore.
If you continue to have issues please let us know!
To setup a DKIM record, I need to create a CNAME record with this Host Name: k2._domainkey
Both my DKIM records are TXT records. I’d get a second opinion about CNAME records…
— sw
Fastmail seems to need DKIM records as CNAME, pointing to their servers. These contain an underscore.
CNAME fm1._domainkey.{mydomain.com} fm1.{mydomain.com}.dkim.fmhosted.com
refer: https://www.fastmail.help/hc/en-us/articles/360060591153-Manual-DNS-configuration
tlambert
Linode Staff
This may be a bug in our system. Our documentation on CNAME records states,
"Enter a string that’s 1-63 characters in length and contains only letters, numbers, and underscores. Hyphens can also be used, but the string cannot start with one."
With this in mind, we've escalated this issue to our Administrators for review. Once we've investigated this more thoroughly, we'll be sure to reach out with an update.
Thanks for the fix, @tlambert! The CNAME version was needed for Mail Chimp. I was already using the TXT version for Google.
Seems like this is still an issue. At least I'm experiencing it too. Trying to add a cname record that Firebase needs me to add.
firebase1._domainkey.MYDOMAIN.com
needs to be going to
mail-MYDOMAIN-com.dkim1._domainkey.firebasemail.com.
Whenever I try to add this I'm getting:
You have entered an invalid target. It must be a valid hostname.
Whenever I remove the _ it allows me to save without issue.
Thoughts?
tlambert
Linode Staff
I was able to add an underscore to the Hostname field of a new record so the hotfix we deployed last week is still working.
However, I received the same message when my entry in the Alias to: field contained and underscore. Since the this field points to the canonical domain, it should not contain an underscore based on Internet Standards RFC 1035.
Because these are the instructions Firebase is giving you, I suggest reaching out to them directly if possible or through one of their Community Channels to get a bit more clarification.
