7 Signs Your Email List Is Killing Your Deliverability

# 7 Signs Your Email List Is Killing Your Deliverability

You can write a perfect cold email. You can nail the subject line, personalise the opener, and nail the CTA. None of it matters if the email lands in spam.

Most deliverability problems aren't caused by bad content or misconfigured authentication — they're caused by list quality. A dirty list doesn't just mean wasted sends. Every unverified address, every spam trap hit, every invalid bounce erodes the sender reputation that took weeks to build.

Here are seven warning signs that your list is working against you — and what to do about each.

1. Your Bounce Rate Is Above 3%

A bounce rate above 3% is a signal most ESPs take seriously. Above 5%, you're at real risk of account suspension or throttling.

Hard bounces — permanent delivery failures to invalid addresses — are the most damaging. They tell receiving mail servers that your list hasn't been cleaned recently, which correlates with spam behaviour.

The fix: Run your list through an email verification tool before any campaign. Remove hard bounces immediately and permanently. If you're pulling contacts from LinkedIn or web scrapes without verification, this step is non-negotiable.

2. You're Getting Spam Trap Hits

Spam traps are email addresses maintained by ISPs and anti-spam organisations to catch senders who don't maintain their lists. There are two types:

You won't know you've hit a spam trap directly — you won't get a bounce notification. Instead, you'll see your inbox placement rate drop quietly over time.

The fix: Never buy email lists. Use only data sources where addresses have been recently active. Age out any contacts you haven't been able to reach in 12+ months before attempting re-engagement.

3. Your Open Rate Has Dropped Without a Content Change

If your subject lines and sending patterns haven't changed but your open rate has fallen 20%+ over 4–6 weeks, the issue usually isn't opens — it's inbox placement. More of your emails are landing in spam, where they never get opened.

Open rate is an imperfect metric (Apple Mail Privacy Protection distorts it), but a consistent downward trend is worth investigating.

The fix: Use a seed testing tool to check actual inbox placement before your next campaign. If you're seeing >15% spam folder placement, pause sending on that domain and audit list quality before continuing.

4. Your Unsubscribe Rate Is High — But Your Spam Complaint Rate Is Low

This sounds counterintuitive. High unsubscribes with low complaints sounds like good news — people are opting out cleanly. But if unsubscribes are consistently above 0.5%, it suggests your targeting is off: you're reaching people for whom the offer has zero relevance.

This matters for deliverability because Gmail and Outlook now factor "move to spam" and "unsubscribe" actions into sender reputation scoring — not just formal complaints via feedback loops.

The fix: Tighten your ICP. If you're emailing a broad list hoping something sticks, deliverability will suffer. More precise targeting means more relevant emails, which means fewer people treating your sends as noise.

5. You're Not Seeing the Same Performance Across Domains

If a campaign to `@gmail.com` addresses performs normally but `@outlook.com` deliverability tanks — or vice versa — that's a domain-specific reputation signal.

Different mailbox providers maintain separate reputation scores for senders. Microsoft's filtering (Outlook, Hotmail) is notoriously aggressive and tends to penalise senders that trigger high complaint rates from their users specifically.

The fix: Segment your list by mailbox provider and look at open rates (imperfect) and reply rates separately. If you see a specific provider underperforming, investigate whether your list has a higher proportion of stale or invalid addresses from that domain.

6. Your Sending Volume Has Grown Faster Than Your Warm-Up

Adding 500 new contacts to a sequence that was previously sending 100 emails per day is an easy way to damage a domain's reputation. Sudden spikes in sending volume are a common spam signal.

Domains need to warm up gradually — most ESPs recommend increasing volume by no more than 20–30% per week when scaling. If you've recently onboarded a new sending domain and scaled too fast, you may already be dealing with the consequences.

The fix: Use a domain warming service before scaling. If you're using Annabot or a similar outreach platform, check the sending limits on your connected email account and build up gradually. Start with your most engaged, high-quality contacts to build positive sending signals before expanding to colder segments.

7. You're Still Using a Primary Business Domain for Cold Outreach

This is the most consequential mistake on the list. Sending cold email from `yourname@yourcompany.com` puts your primary domain at risk. If that domain gets flagged or blacklisted, it doesn't just affect your outbound campaigns — it affects your entire company's email deliverability, including transactional email and customer communications.

Cold outreach should run from a dedicated subdomain or separate domain specifically purchased for outreach purposes. Keep your primary domain clean.

The fix: Set up a separate sending domain (e.g., `outreach.yourcompany.com` or `getyourcompany.io`), configure SPF, DKIM, and DMARC correctly, warm it up before scaling, and monitor its reputation separately.

Putting It Together: A List Health Checklist

Before your next campaign, run through this:

Deliverability is a compounding problem. A small issue ignored for two weeks becomes a serious reputation problem in four. The teams with consistently strong inbox placement aren't doing anything exotic — they're just not cutting corners on list quality.

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Annabot includes built-in email verification on every lead it finds, so your outreach campaigns start with a clean, validated list. [See how it works →](https://annabot.io)