Email deliverability is the practice of getting your messages into the inbox rather than the spam folder or a black hole. It rests on a handful of disciplines: prove who you are with authentication, build reputation slowly, keep your list clean, separate your sending streams, and watch the signals that mailbox providers react to. Do these consistently and the inbox tends to follow.
This is the pillar guide. Each section below stands on its own, and several link out to deeper posts when you want detail.
Authenticate every message
Authentication is the foundation. Without it, mailbox providers cannot tell your mail from a spoof, and modern bulk-sending requirements expect all of it in place.
- SPF publishes which servers may send for your domain.
- DKIM signs each message so receivers can verify it came from you and was not altered in transit.
- DMARC binds SPF and DKIM to your visible From address and tells receivers what to do on failure. Start with a monitoring policy, read the reports, then tighten.
- BIMI is the optional next step once DMARC is enforced: it lets your logo show next to your mail in supporting clients, which reinforces trust.
The setup details and DNS records are in the SPF, DKIM, and DMARC guide. Get this right before tuning anything else, because nothing downstream helps if you fail authentication.
Warm up gradually
A new sending domain or IP has no reputation, and mailbox providers treat unknown senders cautiously. Sending a large burst from a cold setup invites throttling and spam placement. Instead, ramp volume up over time, leading with your most engaged recipients so early signals are positive. The full method is in how to warm up a new email domain.
Keep your list clean
A clean list is the single biggest lever after authentication. Three habits keep it that way:
- Validate at capture. Check addresses for typos and undeliverable domains when people sign up, so junk never enters the list. Bird's recipient validation does this at the point of entry.
- Suppress what you should not send to. Hard bounces, unsubscribes, and complaints belong on a suppression list, and they should stay there. See the suppressions guide for how this works in practice.
- Send based on engagement. Recipients who never open are dead weight that drags reputation down. Reduce frequency to the disengaged, run a win-back, and eventually stop mailing addresses that have gone silent for a long stretch.
Separate marketing and transactional streams
Marketing mail and transactional mail behave differently. Transactional messages (receipts, password resets, confirmations) are expected, opened, and rarely reported. Marketing mail carries more complaint and unsubscribe risk. If they share a sending domain, a rough marketing campaign can drag down the reputation that delivers your password resets.
The usual fix is to send them from separate subdomains, for example a transactional subdomain and a marketing subdomain off your root domain. That isolates reputation so one stream cannot sink the other. The reasoning and setup are covered in email subdomain best practices.
Monitor bounces and complaints
You cannot manage what you do not watch. Two metrics matter most:
- Bounce rate. A rising bounce rate signals list-hygiene problems. Hard bounces should be suppressed immediately; a wave of soft bounces can point to a deeper deliverability issue. For the distinction, read what are bounced emails.
- Complaint rate. This is how often recipients hit "report spam." It is one of the strongest reputation signals, and providers expect it to stay low. A spike means something in your targeting or content needs attention.
Bird's deliverability analytics and the deliverability guide show these signals so you can act before a slide becomes a wall.
Honor unsubscribes
Make opting out obvious and instant. Include a visible unsubscribe link and support one-click list-unsubscribe headers, and process every request quickly. When people cannot find the opt-out, they report you as spam instead, which costs far more than a quiet departure. Treat the unsubscribe link as a feature, not a leak.
Mind content and rendering
Filters read the message, and so do recipients on a cracked phone screen in poor light. A few habits keep both happy:
- Include a plain-text part alongside your HTML.
- Keep a reasonable balance of text to images, and never ship a single-image email.
- Write clean, well-formed HTML and test how it renders across major clients.
- Avoid link shorteners and make sure visible link text matches its destination.
If a specific campaign is underperforming, the related post on why emails go to spam walks through the diagnosis.
FAQ
What is a good bounce rate to aim for?
Lower is always better, and the exact threshold varies by provider. The practical rule: suppress hard bounces immediately, investigate any sustained rise, and keep capturing only valid addresses so the rate stays naturally low. A clean list keeps bounces from becoming a problem in the first place.
Do I need DMARC if I already have SPF and DKIM?
Yes. SPF and DKIM each authenticate part of the picture, but DMARC ties them to your visible From address and gives you reporting plus a policy for failures. Bulk-sending requirements now expect DMARC, so treat it as part of the baseline rather than an extra.
Should transactional and marketing email share a domain?
It is safer to split them onto separate subdomains so their reputations stay independent. A rough marketing send should never be able to delay your password-reset emails. See the subdomain post for how to structure this.
Deliverability is ongoing maintenance, not a one-time setup. Bird's email platform and deliverability tooling are built around these practices, so the signals you need are in front of you as you send.