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    Alibaba Cloud DNS:DNS record conflict rules

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    Alibaba Cloud DNS:DNS record conflict rules

    Last Updated:Jul 30, 2025

    During recursive resolution, different record types have different priorities. If the host record and resolution line are the same, some record types cannot coexist. This is because such a configuration can pose a threat and result in service unavailability.

    Causes of DNS record conflicts

    Assume that you have configured the following two DNS records for example.com:

    Record type

    Host record

    Line

    Value

    MX

    www

    Default

    mx1.hichina.com

    CNAME

    www

    Default

    demo.xxx.com

    According to RFC standards, a CNAME record has the highest priority. During a DNS query, the CNAME record is returned first. This configuration prevents the MX record from being resolved, which affects the email service. In this scenario, Alibaba Cloud DNS detects the DNS record conflict and reports an error to help you avoid this configuration threat. For more information, see RFC1034 and RFC2181.

    Solutions to DNS record conflicts

    If the system reports a DNS record conflict, you can delete the conflicting DNS record or change the host record to resolve the conflict.

    Special handling when the host record is @

    To accommodate various user scenarios, Alibaba Cloud DNS has optimized the conflict rules for some record types when the host record is @.

    When the host record is @, CNAME records and MX records no longer conflict

    Record type

    Host record

    Line

    Value

    MX

    @

    Default

    mx1.hichina.com

    CNAME

    @

    Default

    example.com

    Warning

    This scenario configuration has the risk of mailbox not receiving emails normally or receiving emails intermittently.

    If the localDNS of the mail server prioritizes CNAME type resolution for the @ record, the MX type resolution for the @ record will be affected, resulting in resolution failure or unexpected resolution results.

    When the host record is @, CNAME records and TXT records no longer conflict

    Record type

    Host record

    Line

    Value

    TXT

    @

    Default

    db642353e95243c12d3

    cname

    @

    Default

    example.com

    Warning

    This configuration may cause issues such as failure to receive incoming emails, emails being rejected by recipients, or TXT verification failure. If you encounter these issues, you can remove the CNAME record.

    Complete rules for DNS record conflicts

    The host record is @

    When the host record and resolution line are the same, these different types of resolution records cannot coexist:

    1. ❌: Conflict. The two types of DNS records cannot coexist for the same host record and resolution line. For example, if you have added an A record for example.com, you cannot add a CNAME record for example.com.

    2. ✅: No conflict. The two types of DNS records can coexist for the same host record and resolution line. For example, if you have added an A record for example.com, you can also add an MX record for example.com.

    3. ↔️: Repeatable. Multiple DNS records of the same type can be added for the same host record and resolution line. For example, if you have added an A record for example.com, you can add another A record for example.com.

      NS

      CNAME

      A

      URL

      MX

      TXT

      AAAA

      SRV

      CAA

      SVCB (alias mode)

      SVCB (service mode)

      HTTPS (alias mode)

      HTTPS (service mode)

      NS

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      CNAME

      ✅

      ↔️

      ❌

      ❌

      ✅

      ✅

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      A

      ✅

      ❌

      ↔️

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      URL

      ✅

      ❌

      ❌

      ❌

      ✅

      ✅

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      MX

      ✅

      ✅

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      TXT

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      AAAA

      ✅

      ❌

      ✅

      ❌

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      SRV

      ✅

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      CAA

      ✅

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      SVCB (alias mode)

      ✅

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ❌

      ✅

      ✅

      SVCB (service mode)

      ✅

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ❌

      ↔️

      ✅

      ✅

      HTTPS (alias mode)

      ✅

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ❌

      HTTPS (service mode)

      ✅

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ❌

      ↔️

    The host record is not @

    When the host record and resolution line are the same, these different types of resolution records cannot coexist:

    1. ❌: Conflict. The two types of DNS records cannot coexist for the same host record and resolution line. For example, if you have added an A record for www.example.com, you cannot add a CNAME record for www.example.com.

    2. ✅: No conflict. The two types of DNS records can coexist for the same host record and resolution line. For example, if you have added an A record for www.example.com, you can also add an MX record for www.example.com.

    3. ↔️: Repeatable. Multiple DNS records of the same type can be added for the same host record and resolution line. For example, if you have added an A record for www.example.com, you can add another A record for www.example.com.

      NS

      CNAME

      A

      URL

      MX

      TXT

      AAAA

      SRV

      CAA

      SVCB (alias mode)

      SVCB (service mode)

      HTTPS (alias mode)

      HTTPS (service mode)

      NS

      ↔️

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      CNAME

      ❌

      ↔️

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      ❌

      A

      ❌

      ❌

      ↔️

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      URL

      ❌

      ❌

      ❌

      ❌

      ✅

      ✅

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      MX

      ❌

      ❌

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      TXT

      ❌

      ❌

      ✅

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      AAAA

      ❌

      ❌

      ✅

      ❌

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      SRV

      ❌

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      ✅

      CAA

      ❌

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ✅

      ✅

      ✅

      ✅

      SVCB (alias mode)

      ❌

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ❌

      ✅

      ✅

      SVCB (service mode)

      ❌

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ❌

      ↔️

      ✅

      ✅

      HTTPS (alias mode)

      ❌

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ↔️

      ❌

      HTTPS (service mode)

      ❌

      ❌

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ✅

      ❌

      ↔️