Julien Paltrinieri
If your cold emails are landing in spam, it is almost never random. Mailbox providers score every sender on a small set of signals, and when enough of them look wrong, your mail gets filtered before anyone reads it.
Here is exactly which signals matter, how to check each one, and how to get back to the inbox.
Your domain is not authenticated (SPF, DKIM, DMARC)
Authentication is how a mailbox provider confirms your email actually came from your domain and was not forged. Without SPF, DKIM, and a DMARC policy, Gmail and Yahoo now treat bulk mail as suspicious by default.
Since February 2024, missing authentication is not a soft penalty. An SPF record lists every service allowed to send for your domain. DKIM signing gives each message a cryptographic signature. A DMARC record tells receivers what to do when checks fail. Start DMARC at p=none for monitoring, then tighten once you have a clean read on your authentication posture.
Emailx provides setup guidance for SPF, DKIM, and DMARC as part of onboarding and flags when a connected sending domain is missing authentication before a campaign goes out, so the campaign does not launch into a filter.
You skipped domain warmup, or you are sending too much too fast
A brand new domain, or a real domain that suddenly starts sending 150 cold emails a day, has no sending reputation. Mailbox providers treat a sudden spike in volume from an unknown sender as a classic spam pattern.
Warm up a new domain over two to four weeks, starting with a low daily volume and increasing gradually while maintaining engagement. Keep cold sending volume per inbox conservative and use a separate domain or subdomain for cold outreach so a deliverability problem never touches your main company domain.
Emailx applies sending limits based on domain health stage, so a newer or unwarmed domain is throttled automatically rather than blasted at full volume on day one.
Your list is dirty, and bounces and spam traps are wrecking your reputation
Sending to invalid addresses causes hard bounces, and a high bounce rate is one of the fastest ways to damage sender reputation. Worse, purchased or scraped lists often contain spam traps: addresses that exist only to catch senders who did not collect contacts legitimately.
Verify every list before sending and remove invalid, catch-all, and risky addresses. Keep bounce rate under 2 to 3 percent and complaint rate well under 0.10 percent. Remove non-engagers after a full sequence, and make unsubscribing trivial so unhappy recipients leave quietly instead of marking you as spam.
Emailx imports lead data from Clay, Apollo, Sales Navigator, and CSV sources, and its per-lead research layer helps you send to real, relevant people rather than a broad scraped list, which is the single biggest lever on complaint and bounce rates.
Your copy trips spam filters
Content still matters. Emails heavy with promotional language ("free," "guaranteed," "limited time," "act now," "risk-free"), lots of links, large images, tracking-heavy HTML, or ALL CAPS and excessive punctuation read as marketing blast material to a filter.
Plain text or near-plain-text is far safer. One link at most. Write the way you would email a colleague. Avoid well-known trigger words and let the personalization carry the message.
Emailx generates plain-text-first emails and flags common spam-trigger patterns in the copy before a campaign runs, so drafts that read like a promotional blast are surfaced for a rewrite rather than sent.
Recipients are not engaging, and the filters notice
Modern spam filtering is heavily engagement-based. If your emails are consistently ignored, deleted without being opened, or never replied to, mailbox providers learn that your mail is unwanted and start routing it to spam automatically.
Send to a tight, relevant list so a healthy share of recipients open and reply. Prune non-engagers over time. Deliverability and relevance are the same problem viewed from two angles: the more relevant your sends, the better your placement, which makes your next sends look more credible to the filters too.
Emailx researches each prospect and generates a message specific to them, which lifts engagement, and engagement is what protects long-term inbox placement. Better targeting is a deliverability strategy, not just a reply-rate strategy.
You are missing one-click unsubscribe and other bulk-sender basics
Since February 2024, bulk senders to Gmail and Yahoo must include a one-click unsubscribe header and honor it within a couple of days, send over TLS, and keep authentication aligned.
Missing these does not just risk a compliance issue. A recipient who cannot easily unsubscribe will hit "mark as spam" instead, which is far more damaging than a quiet opt-out. An easy, obvious opt-out in the body means leaving is always easier than complaining.
Emailx handles unsubscribe headers and honors opt-outs automatically, so a recipient who wants out leaves cleanly instead of filing a spam complaint that damages your sender reputation.
You are using the wrong sending setup for cold outreach
Sending cold email from your primary company domain, from a free consumer address, or across a large shared IP with a bad neighbor all create avoidable risk. A deliverability incident on your main domain can hurt your real business email.
Use a dedicated domain or subdomain for cold outreach, kept separate from your main company domain. Warm it properly before running campaigns. Keep per-inbox volume conservative and spread sending across the day rather than in one burst.
Emailx is built for outbound sending, with deliverability guardrails and health-based sending limits, so the sending setup is tuned for cold outreach rather than repurposed newsletter tooling.
Turn research into a real conversation.
Build a campaign, review the message, and decide what sends.
Written by Julien Paltrinieri for Emailx.
