Blog · Email Infrastructure
October 30, 2025 · 7 min read
Few problems in cold email are more frustrating than spam placement. You have invested time in the copy, the list, the infrastructure — and then you check placement rates and find that a third of your emails never reached the inbox. The damage is invisible: you do not know which prospects never saw your email, and they do not know they missed it.
Spam placement is almost never random. There are consistent, identifiable causes, and most of them can be addressed if you know where to look.
The most common technical causes are missing or misconfigured SPF, DKIM, or DMARC records. These authentication signals tell receiving servers that your email is legitimate. Without them, your emails lack the fundamental trust signals that modern inboxes require. Run a check on MX Toolbox or similar to confirm all three are configured correctly for every sending domain.
Sending from a new or under-warmed domain is the second most common technical cause. A domain that has not been properly warmed up has no sending reputation. Mail servers see it as an unknown sender with no history and apply conservative filtering. The solution is patience: warm properly before sending cold.
Spam filters analyse email content for patterns associated with spam: excessive links, trigger words, image-heavy formatting, and HTML that looks like a marketing template. Cold emails should be plain text — no images, minimal or no links, no HTML formatting beyond bold or italic. The email should look like a message from a person, not a campaign from a marketing tool.
Specific words and phrases trigger spam filters: "guaranteed," "free offer," "no obligation," "limited time," and similar phrases that appear in commercial spam. Audit your email templates for these patterns and remove them. Your copy should be specific enough that it could not be sent to anyone other than the intended recipient — which is also, incidentally, what makes it effective.
High bounce rates — anything above five percent — signal to mail servers that your list is dirty. They start treating your domain as a sender who does not maintain their lists, which damages sender reputation over time. Validate every email before it enters a sequence using a tool like NeverBounce or ZeroBounce.
Spam complaints are the most damaging sending behaviour signal. Every recipient who marks your email as spam sends a feedback loop report to the receiving mail provider, which counts against your sender reputation. Keep complaints below 0.1%. The most effective way to do this is to only send to people who fit your ICP tightly — the more relevant the email, the lower the complaint rate.
Use a placement testing tool — GlockApps, Mailreach, or similar — to run your emails through a seed list that tests inbox placement across major providers. This tells you whether your placement problem is specific to Google, Microsoft, or universal. Universal placement problems point to domain reputation. Provider-specific problems often point to content or list quality.
Check your Google Postmaster Tools data if you are sending to Gmail addresses. This dashboard shows your domain reputation, IP reputation, spam rate, and authentication results. It is the most direct window into how Google specifically views your sending domain.