How does Piano ESP search for duplicate stories from previously sent emails
Duplicate articles in email campaigns usually result from changes to existing articles in your RSS feed.
The following tags in your RSS feed are important:
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<guid>: article's unique ID
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<title>: article title
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<category>: article category
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<link>: link to the article
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<description>: short summary or full article text
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<pubdate>: publication date
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<date>: when the article was added to the RSS feed
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<enclosure>: attached object (usually a link to an image)
If you change an existing article's <title>, its <link> may also change. Without a <guid>, Piano ESP treats the story as new, and the recommendation engine may send two similar articles. Similarly, changing the <link> when no <guid> is specified will cause the system to consider the article new.
<guid> is an optional tag used as the article's ID. If the feed lacks <guid>, our system uses <link> to identify the article. If <guid> is absent and <link> changes, the system will treat the story as new.
To prevent duplicates, include a reliable <guid> tag in your RSS feed so the article remains identifiable despite other tag changes.
When you modify an existing article, update the <date> tag. If you do not have <date>, update <pubdate>.
Piano ESP searches for duplicate stories by looking back at up to four previous emails sent to the user within the past 30 days across all campaigns.
If you send more than four emails in a short period, the system may reselect recently sent articles (for example, sending more than four emails per day increases the chance of duplicates).
This behavior is controlled by the Exclude stories sent previously setting in Dynamic block settings. It is enabled by default.
Note that ESP does not check duplicates against stories added more than 45 days ago. Avoid adding articles that duplicate content from items older than 45 days, as the system will not match those duplicates.