What’s the difference between global and user-level filtering?
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You send a campaign and check the results. Opens look fine overall, but a handful of recipients never see your emails at all. Are you blocked everywhere, or is it just a few people marking you as junk? The answer matters a lot, because the fix is completely different depending on which one you're dealing with.
Global filtering is a decision made by the mailbox provider for every single one of their users. If Gmail decides your sending domain or IP is a threat, nobody on Gmail gets your mail. Full stop. These rules usually come from things like blocklist hits, failed authentication signals, high complaint rates, or known spam patterns. Global blocks are the bluntest instrument in filtering.
User-level filtering is personal. It's built from what an individual subscriber actually does with your emails. Open often, and their filter learns you're someone worth showing. Delete without reading a few times, and you quietly slip toward the spam folder for that person specifically. Gmail leans heavily into this, which is why the same email from the same sender can land in the inbox for one recipient and spam for another.
Outlook does something similar through its Focused Inbox feature, routing mail it thinks you care about into the main tab and everything else into "Other". It's not technically a spam folder, but it has the same effect on your open rates.
How to tell which one you're dealing with: If opens drop sharply across an entire mailbox provider at the same time, that points to a global problem. If you see mixed results at a single provider (some people opening, some not), user-level filtering is the more likely culprit. Seed testing tools and inbox placement monitors can help you check this without relying on your subscribers as guinea pigs.
Global blocks are harder to recover from, but not a dead end. Fixing the underlying cause (authentication gaps, a dirty list, a spike in complaints) is the first step. Then you typically need to go through a formal postmaster process or a mitigation request to the provider. User-level filtering is more forgiving. Better content, better segmentation, and giving disengaged subscribers a real chance to opt out all help over time.
If you're not sure where to start, our free blocklist checker can tell you in seconds whether your domain or IP is showing up on any major blocklists. And if things are actively broken right now, the SOS hotline is free and we actually pick up.
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