DNS conflicts are caused by overlapping DNS records. If DNS records overlap, the conflicting DNS records will either not at all or only partially function.
If you add a DNS record that conflicts with other DNS records of an active service, a warning will be displayed.
DNS conflicts can arise in the following cases:
A CNAME record conflicts with a TXT, MX, AAAA, A, or existing CNAME record, and all other records of this type conflict with an existing CNAME record. In principle, no further DNS records such as TXT, MX, A or AAAA records may be configured for an alias in a CNAME record.
In the following example, the subdomain www.example.com is connected with the static IP address 192.0.2.42. Furthermore, the subdomain www.example.net is connected to the IP address 192.0.2.45. The CNAME record defines www.example.net as the alias for www.example.com. This CNAME record leads to a conflict because the subdomain www.example.net is already connected to the IP address 192.0.2.45:
www.example.com. IN A 192.0.2.42
www.example.net IN A 192.0.2.45
www.example.net. IN CNAME www.example.com.
The NS records entered are in conflict with the other DNS records. This applies to the same host and to any record that ends with the NS host.
Example: The NS record ns1.example.com conflicts with DNS records (for example, TXT, MX, AAAA, A records) for example.com, www.example.com, shop.example.com, or forum.example.com.
MX records for an active service conflict with all other MX records for the same host or subdomain.
A and AAAA records for an active service such as Plesk conflict with all other A and/or AAAA records for the same host or subdomain.
Example: Plesk has created an A record for the domain example.com that points to 192.0.2.42. If you configure an A record for this domain that points to IP 220.127.116.11, these two A records conflict.