What Is Email Deliverability and Why Does It Matter for Recruiters?
Email deliverability is the ability of your emails to land in the recipient’s inbox, not the spam folder. For recruiters, this isn’t just a technical metric—it directly affects your ability to reach candidates, clients, and partners.
If your outreach emails never arrive or get flagged as spam, your pipeline slows down before it even starts. Whether you’re sourcing passive candidates or following up with hiring managers, poor deliverability can quietly sabotage your efforts. Here’s what recruiters need to know about how it works, why it breaks, and how to fix it.
How email deliverability works
Every time you send an email, email service providers (like Gmail or Outlook) evaluate whether it’s safe, relevant, and legitimate. They look at signals like:
- Your domain reputation: Has your domain been flagged for spam in the past?
- Authentication protocols: Are SPF, DKIM, and DMARC properly set up?
- Engagement signals: Do people open, reply to, or delete your emails?
- Sending patterns: Are you sending too many emails too fast from a new domain?
If any of these raise red flags, your messages may get filtered into spam or blocked entirely.
Why recruiters are especially vulnerable
Recruiters rely heavily on outbound email, often at scale. That puts them in a similar category as sales teams—high-volume senders who often contact people for the first time. Here’s where problems typically start:
- New domains or inboxes: An inbox needs to be warmed up before sending cold outreach.
- Low engagement: If too many emails go unopened or unanswered, your sender reputation suffers.
- Spammy language: Phrases like “Work from home opportunity” or “Urgent hiring now” can trigger filters, even if your message is legit.
How to Protect Your Outreach and Improve Deliverability
You don’t need to be a technical expert to fix deliverability problems. Here’s what to focus on:
Warm up new inboxes gradually
Use a tool like WarmupInbox to simulate real conversations and build trust. Start with 10–20 emails per day, then increase slowly over a few weeks.
Authenticate your domain
Make sure SPF, DKIM, and DMARC records are correctly set up. These tell email providers your messages are legitimate.
Track engagement and adjust
Monitor open and reply rates. If you notice a drop, pause sending and investigate. Avoid sending to stale or purchased lists.
Avoid spam triggers
Steer clear of all-caps subject lines, excessive exclamation marks, or misleading offers. Tools like Mail-Tester can help.
The Pre-Send Checklist: Your Deliverability Foundation
This pre-send checklist helps you lay the foundation for strong deliverability. It covers the technical setup, domain reputation, and warm-up steps you need to complete before launching any outbound sequence.
1. Set up authentication protocols correctly
Email authentication tells receiving servers, “This email is legit.” Without it, your messages look suspicious. There are three protocols you need to configure:
- SPF (Sender Policy Framework): Lists which IPs are allowed to send email for your domain.
- DKIM (DomainKeys Identified Mail): Adds a digital signature to prove the message wasn’t altered.
- DMARC (Domain-based Message Authentication, Reporting & Conformance): Tells receiving servers what to do if SPF or DKIM checks fail.
2. Warm up your domain and inbox gradually
If you start sending 100+ cold emails per day from a brand-new domain, you’ll trigger spam filters fast. Start slow: Send 10–20 emails per day, then gradually increase over 3–4 weeks using a warm-up tool.
3. Check your domain reputation and blacklist status
Before sending anything, check if your domain or IP is on any blacklists. Use WarmupInbox’s blacklist monitoring or tools like MultiRBL or MXToolbox. If you’re listed, follow the removal instructions.
Crafting the Right Message: Content & Structure
The right message builds trust, signals relevance, and avoids spam triggers. This section breaks down how to structure your cold emails for deliverability and engagement, from subject line to signature.
Write like a human, not a template
Spam filters and recipients can both spot a generic message. If your email looks copied and pasted from a sales playbook, expect low engagement and higher spam risk.
“Hi [First Name], I wanted to reach out and see if you’re interested in a cutting-edge solution that will revolutionize your workflow.”
“Hey [First Name], saw your team just launched [Product]. Curious if you’re exploring ways to scale outreach without hurting deliverability.”
Structure for clarity and engagement
A cold email should be easy to scan. Use this structure:
Subject: Quick question about your outbound team Hey [First Name], Noticed your team’s growing fast. Are you handling cold outreach in-house or using a platform? I help B2B teams improve inbox placement and avoid blacklists while scaling outreach. Worth a quick chat? — [Your Name] Deliverability Specialist, [Company] [LinkedIn or website]
Smart Sending: How and When You Hit ‘Send’
Sending too fast, too often, or at the wrong times can trigger spam filters and hurt your sender reputation. Smart sending is about timing, volume, and behavior that aligns with how real humans send email.
Match sending behavior to your domain’s reputation
Your domain’s age, history, and current reputation should shape your sending strategy. A fresh domain needs a slow warm-up, while a seasoned domain can handle higher volume.
| Domain Type | Daily Volume Cap (initial) | Warm-up Duration | Notes |
|---|---|---|---|
| New domain | 10–20 | 4–6 weeks | Needs full warm-up before outreach |
| Dormant domain | 20–50 | 2–3 weeks | Resume gradually with monitoring |
| Warm domain | 50–200+ | Ongoing | Monitor health and engagement |
Final Checklist: Your 5-Point Deliverability Audit
Before any high-volume campaign, run this quick audit. This checklist covers the most common reasons emails land in spam.
- Check domain and inbox reputation: Keep your spam complaint rate under 0.1% and your bounce rate under 2%.
- Review DNS and authentication settings: Confirm SPF, DKIM, and DMARC are configured correctly.
- Scan for blacklist appearances: Run a blacklist check weekly and follow delisting instructions if needed.
- Analyze your email list quality: Stop using purchased lists and verify your contacts before sending.
- Review your message content: Use natural, human language and avoid spam trigger words.
FAQ
Why do I need to warm up a new email domain?
When you send from a fresh domain, mailbox providers don’t trust you yet. A proper warm-up gradually builds trust by starting with low volume, increasing over time, and generating positive engagement signals like opens and replies.
How long should I warm up my inbox before sending cold emails?
A typical warm-up period lasts 2–4 weeks. If you’re planning to send high volumes (500+ per day), give it more time—up to 6 weeks. Keep the warm-up running in the background to maintain your reputation.
What causes emails to land in spam even after warming up?
Warming up helps, but it’s not a silver bullet. Spam placement can still happen if you’re sending to low-quality lists, your content triggers spam filters, you’re missing authentication records, or your domain is on a blacklist.
