使用配置了 DMARC 發送 RUA 的子域時，是否需要添加 DMARC 報告 TXT 記錄？

username@subdomain.example.com如果我從的rua=username@example.comDMARC 記錄中發送電子郵件subdomain.example.com，是否需要創建 DMARC 報告 TXT 記錄（例如，subdomain.example.com._report._dmarc.example.com TXT "v=DMARC1"）？

不，不是根據RFC：

When a Mail Receiver discovers a DMARC policy in the DNS, and the
  Organizational Domain at which that record was discovered is not
  identical to the [Organizational Domain][2] of the host part of the
  authority component of a [URI] specified in the "rua" or "ruf" tag,
  the following verification steps are to be taken:

1.  Extract the host portion of the authority component of the URI.
      Call this the "destination host", as it refers to a Report
      Receiver.

2.  Prepend the string "_report._dmarc".

$$ 2 $$ https://www.rfc-editor.org/rfc/rfc7489#section-3

引用自：https://serverfault.com/questions/1055805