bramble.co, a real published series. Every name is invented.

Which send did it?

Google already published the answer. It just printed it as a string.

0.30%
0.10%
1.74%Abandoned Cart · Email 2
Jul 12grey ribbon: the domain · stems: each send Google graded · red: one flowSep 1
  1. 01

    Google graded 26 send-days in this window and printed a string for each.

    The strings are Klaviyo's own ids, the campaign id and the flow message id it puts in every email's Feedback-ID header. Postmaster prints them bare and stops.

  2. 02

    Klaviyo ships no screen that turns a string back into a name.

    The header exists so Gmail can report on the send. Nothing in Klaviyo reads the report back.

  3. 03

    Joined, one flow carried 78.3% of the window.

    Abandoned Cart, 21 of 26 days over the line, worst 1.74% on one day. The domain's own line never rose above 0.28%.

Google names the send, never the person. A string we cannot match stays unmatched, and we say so.

Every sentence above, in Google and Klaviyo’s own words.4 sources, each dated
  • Feedback-ID: a:b:c:SenderId

    Google · Feedback Loopread 2026-08-15

  • All emails sent from Klaviyo will automatically include a header called Feedback-ID.

    Klaviyo · Academyread 2026-08-15

  • For a given day's traffic, FBL reports are generated only if a given Identifier is present in a certain volume of mails as well as in distinct user spam reports.

    Google · Feedback Loopread 2026-08-15

  • The spam rate is the percent of your messages that are delivered to engaged recipient's Inbox and then marked as spam by the recipient.

    Google · Postmaster Toolsread 2026-08-15

NextKlaviyo says 0.01%. Postmaster says 0.33%.