DNS Management on Lightsail

When setting up email authentication (like SPF, DKIM, or DMARC) in Amazon Lightsail's DNS management, you might encounter challenges with certain record formats, especially those requiring underscores in the hostname.

Unfortunately, Amazon Lightsail's DNS hosting has limitations regarding certain characters in DNS records. Specifically, underscores are not allowed in CNAME record hostnames according to RFC 1035, which only permits letters, digits, and hyphens in domain names.

However, TXT records in Lightsail do support underscores. If your email authentication system requires a TXT record with a specific format, you should be able to create this in your Lightsail DNS zone.

Here are some options to consider:

1. If possible, use a TXT record instead of a CNAME record for your email authentication.

2. If you absolutely need to use record formats that Lightsail doesn't support, you might need to consider using a different DNS provider, such as Amazon Route 53, which supports more DNS record types and has fewer restrictions.

3. You can keep your domain registered with Amazon but use another service for DNS hosting if necessary.

4. Contact your email service provider to see if they offer alternative authentication methods that are compatible with Lightsail's DNS limitations.

Remember that DNS changes can take up to 48 hours to propagate globally, so allow time for any changes to take effect.
Sources
Lightsail dns hosting not accepting cname | AWS re:Post
Route domain traffic to a Lightsail instance - Amazon Lightsail

Create a DNS Zone if you don't have one for that particular domain, then add the relevant TXT record under records.

Here is the step by step from AWS Lightsail Documentation: https://docs.aws.amazon.com/lightsail/latest/userguide/lightsail-how-to-create-dns-entry.html

Hi,

If I am understanding your question correctly, you need to set a TXT record for the apex domain. You can do this by using @ for the subdomain in the Record name field. This will create a record that points to your root domain.