Key takeaways
- Deliverability is the share of your email that reaches the inbox rather than spam or nowhere at all, and it decides whether the rest of your email program pays off.
- Mailbox providers have tightened the rules. Google and Yahoo began enforcing bulk sender requirements in February 2024, and Microsoft required SPF, DKIM and DMARC from senders of more than 5,000 emails a day to Outlook.com addresses starting May 5, 2025.
- Google’s sender guidelines ask bulk senders to keep reported spam rates below 0.1% and never reach 0.3%, and to offer one-click unsubscribe.
- Most spam-folder problems trace back to missing authentication, poor list quality, sudden volume spikes or content and links that look risky.
- Monitor Google Postmaster Tools, bounce and complaint rates, and fix the cause rather than switching platforms.
You wrote a strong email, tested the subject line and segmented the list, and a chunk of subscribers still never saw it because it landed in spam. Deliverability problems are common and usually fixable. This Emulent guide covers the principles that get email into the inbox, how to apply them to your business and how to monitor and improve deliverability over time.
What principles keep your emails out of spam?
Prove who you are, send to people who want your mail and behave consistently.
| Principle | What it means in practice |
|---|---|
| Authenticate your domain | publish SPF and DKIM records for every service that sends on your behalf, and a DMARC record aligned with your From address. Google’s email sender guidelines require these for bulk senders. |
| Meet the major providers’ rules | Microsoft announced on its Outlook blog that domains sending more than 5,000 emails a day must pass SPF, DKIM and DMARC, with non-compliant mail routed to junk and later rejected. |
| Keep complaints low | send only to people who opted in, make unsubscribing easy with a one-click header and a visible link, and remove complainers immediately. |
| Clean your list | remove hard bounces right away, suppress long-inactive subscribers after a re-engagement attempt and never buy or rent lists. |
| Send consistently | avoid sudden jumps in volume. Warm up new domains and IP addresses gradually. |
| Use a sending subdomain | for example, a mail subdomain for marketing, so problems do not affect your main domain’s business email. |
| Keep content clean | avoid link shorteners and misleading subject lines, use a healthy balance of text and images and make sure every link goes to a secure, working page. |
Emulent applies one test to every send: would recipients recognize the sender and be glad to receive it? Mailbox providers increasingly judge mail by that same standard, through complaints and engagement.
How do you apply deliverability best practices to your business?
The rules are the same for everyone; the risks differ.
- B2B companies: corporate filters are strict. Avoid cold-emailing large purchased lists from your main domain, and keep sales outreach volumes modest and personal.
- Franchise brands: centralize authentication and list rules so one location’s poor practices cannot damage the shared domain.
- Small businesses: even low-volume senders benefit from SPF, DKIM and DMARC. Make sure your email platform and your website contact forms are included in your SPF record.
- Healthcare email: use platforms that support your HIPAA obligations for patient communications, and keep marketing lists separate from clinical messaging.
- Ecommerce: large promotional bursts during holidays can trigger filtering, so increase volume gradually ahead of peak season. For ecommerce, Emulent recommends Shopify; Shopify Email and connected platforms provide domain authentication settings to complete.
Website forms matter too. On WordPress sites Emulent builds, we send form notifications through an authenticated email service rather than the server’s default mail function, and add spam protection so bots cannot fill your list with fake addresses.
How do you monitor and improve deliverability?
Watch the signals mailbox providers use, and act early.
- Google Postmaster Tools: shows your spam complaint rate, domain reputation and authentication results for Gmail recipients.
- DMARC reports: reveal which services send mail as your domain and whether they pass authentication. Move from a monitoring policy to quarantine or reject once everything legitimate passes.
- Bounce rates: rising hard bounces point to list quality problems; soft bounce spikes can signal throttling.
- Complaint and unsubscribe rates by campaign: spikes show which content, frequency or segment is causing problems.
- Inbox placement tests: seed tests with tools such as GlockApps or your platform’s deliverability features show where mail lands across providers.
- Engagement by provider: a sudden drop in clicks from one provider, such as Gmail or Outlook, often means a filtering problem there. Use clicks, since Apple Mail Privacy Protection inflates opens.
- Blocklists: check major blocklists if bounces mention blocking, and fix the cause before requesting removal.
Good deliverability also depends on sending content people want, which ties email back to your wider content strategy.
How can the Emulent team help?
Emulent audits deliverability, sets up SPF, DKIM and DMARC, cleans lists, configures sending subdomains and monitors reputation over time. A caveat: recovering a damaged sender reputation can take weeks of careful, lower-volume sending, so start with your most engaged subscribers and expand gradually. Contact the Emulent team to get your emails back into the inbox.