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Inbox providers use complex, private systems to classify incoming mail. While specific rules aren't published, consistent patterns are clear: strong sender reputation, healthy lists, and relevant content lead to better inbox placement. Poor reputation, low engagement, and technical issues increase the odds of spam filtering.
Your domain and IP trustworthiness
Subject lines, body copy, and structure
How recipients interact with your emails
Reputation, content, and engagement work together.
Sender reputation reflects how trustworthy your domain and IP appear to inbox providers. It's driven by measurable signals and determines if messages reach the inbox or the spam folder.
Opens, clicks, replies, and positive interactions.
Predictable schedules beat sudden spikes.
Keep hard bounces near zero and total bounces low.
Keep well below 0.1% per send.
Make it easy to opt out; high rates signal poor fit.
Filters examine subject lines, body copy, HTML structure, and links. Aim for clarity over tricks.
Avoid all caps, excessive punctuation, and manipulative phrases.
Use a healthy text-to-image balance; include alt text.
Limit link count and domains; prefer your own domain.
Keep HTML clean; avoid heavy inline styles and pasted formatting.
Use simple personalization to increase relevance.
Include a visible opt-out (top and bottom if possible).
Inbox providers weigh how recipients react to your messages. Focus on mailing people who interact with your brand and reduce broad sends to disinterested audiences.
Watch leading indicators and act early when trends shift.
Hard bounces should be near zero.
Investigate spikes immediately.
High rates signal content or targeting issues.
The most reliable way to avoid spam filtering is to protect reputation before sending. Our app reduces risk in real time by filtering poor-quality addresses and surfacing deliverability signals for smarter targeting.
We block invalid and risky addresses before they receive any mail, cutting down bounces and the chance of spam complaints.
Deliverability scores and webhook events let you build segments of high-quality contacts to mail first, which improves engagement and inbox placement.
Rarely. Reputation is foundational; content helps, but fixing list quality and sending habits comes first.
They provide direction, not guarantees. Validate with real engagement from your actual audience.
There is no fixed timeline, but if you apply the steps above consistently, most senders see inbox placement improve over the following weeks as reputation and engagement recover.
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