When adding a DKIM record for AWS in your Namecheap domain DNS settings, you may encounter an error if the DKIM name (host field) exceeds the allowed length. According to Namecheap DNS limits, the Host field for TXT records is limited to 60 characters, including digits and characters. AWS sometimes generates DKIM selectors that, when combined with _domainkey and your domain, exceed this limit, causing the error.
To resolve this, first double-check the DKIM selector provided by AWS. The selector itself (the part before ._domainkey) should be relatively short. In Namecheap’s DNS panel, you only need to enter the selector and _domainkey in the Host field, not the full domain. For example, if AWS gives you a DKIM record for abcdefghijklmnopqrstuvwxyz1234567890._domainkey.example.com, you should enter abcdefghijklmnopqrstuvwxyz1234567890._domainkey as the Host. If the selector AWS provides is too long, you may need to generate a new DKIM key in AWS with a shorter selector, as AWS allows you to specify the selector name when creating DKIM keys.
If AWS only provides long selectors and you cannot shorten them, Namecheap’s DNS will not support these due to the 60-character limit. In this case, you have two options: either use a shorter selector in AWS or consider using a different DNS provider that supports longer hostnames for TXT records. If you need step-by-step help generating a new DKIM key in AWS with a shorter selector, let me know, and I can guide you through that process.
For more details on Namecheap DNS limits, you can review the following link: