Skip to main content

Update to Date-based Entry Ignoring

TL;DR FeedMail will now ignore new items 7 days older than a previously seen item. This is expected to affect almost no "true" new posts.

In theory checking to find new entries for a feed is a simple process.

  1. Download the feed.
  2. Check the ID of each entry to see if you have seen it before.

However the real world is much messier. It is recommended for feed IDs to be URLs (to ensure global uniqueness) however this results in many feeds just using the URL that the article is available at. However these URLs sometimes change, and poorly designed feed generators update the ID of existing entries to the new URL.

From a protocol point of view these are completely new entries, however to a user these are duplicates. In order to reduce the effect of this common issue on our our users FeedMail has some simple mitigations for posts that have recorded published dates.

  1. If the entry is older than a year always ignore it.
  2. If the entry is older than the 10th newest post in the feed ignore it.
  3. If the entry is more than 7 days older than the newest post in the feed ignore it.

Rule number 3 is a new rule to better filter out old entries for infrequent feeds. In many cases this will ensure that you only receive one or two duplicate entries if the feed accidentally changes their post IDs.

One might think that you can simply ignore any article that isn't newer than the newest article, however in practice many feeds post items with the published timestamp slightly out of order. Based on our analysis a 7 day window will almost never ignore new articles while filtering out a lot of duplicates with new IDs.

Labels:

Comments

Post a Comment

Popular posts from this blog

Delivery Delays to Gmail

In the past 48 hours Google has started delaying the delivery of some FeedMail notifications. This is currently affecting about 10% of messages to Gmail users. These notifications will be resent with a delay. We also speculate that some notifications will be marked as spam.   Update : As of 2023-05-09 this appears to be resolved. If You Are Affected If you use Gmail you may be affected by this. Notifications may be delayed or marked as spam. If your notifications are marked as spam you can create a filter to avoid this. Use "from:*@feedmail.org" as the rule and select " Never send it to Spam". If your notifications are delayed we are unaware of any action that you can take. However marking notifications that ended up in your spam folder as "Not Spam" may help avoid future delays.  It does appear that these emails are eventually being accepted but we are unsure if that means that they are actually ending up in users' mailboxes (or even their spam folder
Post a Comment
Read more

Updates to HTML Processing

Since its inception FeedMail has done processing on HTML content in feeds to ensure that it renders as expected in email form. At first this was fairly simple things like rewriting URLs to point to the correct location (many feeds use non-absolute URLs that won't work in email) but over time more complex transformations were added such as adding fallback content to media embeds without any. The full-text scraping feature requires even more complex processing as it requires stripping away most of the page and handling content that was designed for full-featured browsers. What changed? Recently FeedMail has migrated all HTML rewriting to use new infrastructure. This provides more flexibility and enabled new features (such as showing controls on all media embeds) and made our processing much more reliable. What does this mean to me? As a user you shouldn't see much difference. Overall the emails you receive should be better formatted but the difference will be subtle. Full-text sc
Post a Comment
Read more

Email Headers

FeedMail now sets some email headers that advanced users can use to filter the messages that FeedMail sends. For example you can filter notifications in a specific category into a different folder. The headers that we set are documented in the FAQ . These headers have been being set on notifications for a few months now so you can use past messages to test your filters. If you have any questions, or would like to see other headers set to help your filtering please let us know .
Post a Comment
Read more