Email Deliverability: What It Is and How to Protect It

Deliverability is the ability of your emails to reach the inbox rather than the spam folder. A delivered email (one that didn't hard bounce) might still end up in spam — this is called an inbox placement problem.

Inbox providers (Gmail, Outlook, Yahoo) use a combination of technical authentication, sending reputation, and engagement signals to decide where your email lands.

These three DNS records are the foundation of email authentication:

SPF (Sender Policy Framework): lists the servers authorised to send email on behalf of your domain. Without it, inbox providers treat your email with suspicion.

DKIM (DomainKeys Identified Mail): adds a cryptographic signature to every email. Inbox providers verify the signature to confirm the email wasn't tampered with in transit.

DMARC (Domain-based Message Authentication, Reporting & Conformance): tells inbox providers what to do if SPF or DKIM fails (none / quarantine / reject) and sends you reports on authentication failures.

All three should be set up for your sending domain. Your ESP (Klaviyo, Mailchimp) provides DNS records to add to your domain registrar. Check your status in Email → Deliverability → Authentication.

Your sending reputation is a score maintained by each inbox provider based on:

• Spam complaint rate: above 0.1% triggers Gmail throttling; above 0.3% can cause blocks
• Hard bounce rate: above 2% signals low-quality lists
• Engagement rate: high open and click rates signal wanted email; low engagement signals unwanted
• Sending volume consistency: large sudden spikes in volume trigger spam filters

Monitor your reputation in Email → Deliverability → Reputation. AskBiz pulls data from Google Postmaster Tools (for Gmail) and Microsoft SNDS (for Outlook) if you connect these in Settings.

Inbox placement testing sends your email to seed addresses at major inbox providers and measures whether it lands in inbox, spam, or promotions tab.

Tools: GlockApps, Litmus, 250ok. AskBiz integrates with GlockApps — connect your account in Settings → Integrations → GlockApps and then run a placement test from Email → Deliverability → Inbox Placement.

Run a placement test:

• Before sending to a new large segment for the first time
• If spam complaint rates have recently increased
• After changing your sending domain or ESP

If you switch ESPs or start sending from a new subdomain, you must warm the IP/domain gradually. Inbox providers have no reputation history for new senders — sending large volumes immediately will trigger spam filters.

Warming schedule example:

• Week 1: 200 emails/day to your most engaged subscribers
• Week 2: 500/day
• Week 3: 2,000/day
• Week 4: 5,000/day
• Week 5+: scale to your target volume

Always start with your most engaged subscribers — good engagement signals during warming build reputation quickly.

1. Clean your list regularly: remove hard bounces immediately, suppress inactives every 6 months

2. Use sunset policies: stop emailing subscribers who haven't opened in 180 days

3. Honour unsubscribes within 10 business days (legally required in UK, US, EU)

4. Don't use misleading subject lines: 'RE:' or 'FWD:' prefixes on non-reply emails increase spam complaints

5. Send consistently: sporadic large sends look suspicious; a regular cadence builds trust with inbox providers

6. Monitor complaint rates daily: set an alert in AskBiz at Email → Deliverability → Alerts for complaint rate > 0.08%