All domains registered with 1&1 IONOS are automatically assigned a _domainconnect _domainconnect.1and1.com) CNAME record. This DNS record simplifies the connection between a domain at 1&1 IONOS and an external website hosted by third party website services or e-shop providers using the Domain Connect protocol.
The Domain Connect protocol is an open standard which automatically connects a domain to an external website. For you as a user, this has the advantage that you can easily connect your domain to third party websites and e-shops without having to worry about the DNS settings.
The _domainconnect record has no effect on your other DNS settings. You can create additional CNAME records as needed. We recommend that you do not delete this CNAME record, otherwise your 1&1 IONOS domain will no longer support the Domain Connect protocol.