TL;DR: Deliverability — whether your email lands in the inbox or spam — comes down to four things: authentication, domain reputation, list quality and content. Get authentication right first (it's the foundation and the most common failure), then protect your reputation with clean lists and genuine engagement. Scan your domain free to check your authentication in seconds.
1. Authentication — the foundation
If your SPF, DKIM and DMARC aren't right, nothing else matters — mailbox providers distrust you before they even read the message. This is the single biggest, most fixable deliverability lever, and since 2024 Google and Yahoo require it. Start here: confirm all three pass and DMARC is moving toward enforcement.
2. Protect your domain reputation
- Warm up new domains/IPs — ramp volume gradually rather than blasting from day one.
- Use a consistent From domain so receivers build a stable reputation for it.
- Consider a subdomain for bulk/marketing mail to keep it separate from your transactional mail.
3. Keep your list clean
- Only email people who opted in. Purchased lists wreck reputation fast.
- Remove hard bounces and inactive contacts regularly — high bounce rates and spam complaints are the fastest way to the junk folder.
- Make unsubscribing easy (and include one-click unsubscribe for bulk) — it's better than being marked as spam.
4. Mind your content
- Avoid spam-trigger formatting: ALL CAPS subjects, too many exclamation marks, link-only emails, misleading subjects.
- Keep a healthy text-to-image ratio and always include a plain-text version.
- Send relevant mail people actually open — engagement (opens, replies) is now a major signal.
5. Monitor and maintain
Turn on DMARC reporting to see who's sending as you, watch your bounce and complaint rates, and re-check your authentication whenever you add a new sending tool — a new CRM or newsletter often breaks SPF.
FAQ
What's the single biggest deliverability factor?
Authentication. Missing or broken SPF/DKIM/DMARC is the most common reason good mail goes to spam, and it's the easiest to fix.
How long does it take to fix bad deliverability?
Authentication fixes take effect in hours. Rebuilding a damaged reputation takes weeks of consistent, clean sending.
Do I need a separate domain for marketing email?
Not required, but a subdomain for bulk mail keeps any reputation issues away from your important transactional and personal email.
Want to know if your authentication is holding you back? Scan your domain, then reply to your report — we're developers and we'll get your SPF, DKIM and DMARC right so your mail reaches the inbox.