Deliverability isn't only about infrastructure. Email content itself triggers filters. A well-authenticated, warmed, reputation-clean sender can still land in spam because of content patterns that match spam fingerprints. The safer your content, the better your placement.
Look at the whole email and score likelihood of spam based on patterns learned from billions of examples. The more spam-like your content, the higher the score.
Check for specific flags: certain phrases, structural patterns, link ratios. Older but still active.
Both exist. Both matter.
Ironically, patterns that became common in cold email are now flagged:
These aren't always fatal, but overuse patterns them as templated outreach.
"SAVE BIG NOW!" = instant spam signal. Use normal capitalization. Emphasis via bold is fine; all-caps isn't.
"Click now!!!" Every extra punctuation mark adds spam score. One exclamation maximum per email.
More than 2-3 links in a short cold email triggers filters. Especially bad: multiple links to different domains.
An email that's 90% image with minimal text signals spam (images can hide spammy content from text-based filters). For cold email, stick to plain text or very light HTML.
A marketing-style HTML template (logo, images, multi-column layouts, footer graphics) signals bulk email. Cold email should look like a person typing a personal message.
If the ratio of link text to body text is high, filters flag it. A 40-word email with 5 links is suspicious. A 150-word email with 1 link is fine.
bit.ly, tinyurl, even t.co in emails triggers filters (spammers use them to hide destinations). Use direct URLs.
Single tracking pixel is fine. Multiple pixels, unusual tracking parameters, or obvious open-tracking can flag.
Write your cold email. Now imagine printing it and mailing it. Does it look like something a real person writes to another real person? Or does it look like a flyer?
If flyer: strip design, shorten, remove marketing language, make it plain text.
For cold B2B, plain text or very minimal HTML (one link, one bold emphasis) consistently outperforms designed HTML emails on:
The reason: plain text signals "person writing to me" not "marketing broadcast."
Subject lines are the first filter-check point. Triggers:
See subject lines for positive patterns.
Attachments in cold email:
Don't attach files to cold emails. If you need to share a document, link to a cloud-hosted version or mention you'll send it after reply.
Long legal disclaimers, unsubscribe instructions with multiple links, privacy policy boilerplate, mark emails as marketing-style. Keep footers brief: name, title, company, optional brief unsubscribe sentence.
Sending the exact same email to thousands of recipients pattern-matches spam. Use spintax (variable text) to ensure each message is slightly different, even for the same campaign.
Signatures with LinkedIn, Twitter, website, phone, calendar, looks corporate/marketing. Simpler signatures win.
Send your email to a given address. Get a score 1-10 with breakdown of issues. Aim for 9+.
Test placement across multiple providers. Shows inbox/promotions/spam for each.
Create test email addresses at Gmail, Outlook, Yahoo, etc. Add them to your test sends. Check placement for each.
Close your laptop. Imagine opening an email inbox. Would the email you just wrote make you pause or make you delete immediately?
If it would make you pause as a recipient: probably good content. If it looks like every other "hope this email finds you well" cold pitch you delete without reading: rewrite.
Next: Monitoring inbox placement.