Situation:
You're verifying a mail service like Klaviyo, ConvertKit, Mailchimp, or another ESP and they've requested you add CNAME records to validate your domain.
Problem:
You receive an error message saying:
Warning: The canonical name <the subdomain you just added>. does not resolve to an A or AAAA record.
Solution:
No changes are needed. You've likely entered everything correctly. Plesk is warning you that the subdomain you've created with the CNAME record doesn't point to an A or AAAA record, because instead the referenced CNAME points to a location that only has a TXT record (which is all that is needed for SPF, DKIM, DMARC, etc).
Please wait 5-30 minutes and attempt to verify the domain with your ESP, they should pick up the records and validate the domain without trouble. If they do not, please double-check the added records and/or open a ticket for support.
