Email deliverability is whether messages reach the intended inbox. Check authentication, sending reputation, audience consent, and message content when delivery or placement changes.
If delivery changes, start with authentication results and provider events.
Then inspect complaints, bounces, recent volume changes, audience source, and the final message. The table identifies who can investigate each part.
Deliverability infrastructure map
Use provider logs for delivery failures and your own contact records for audience and consent checks.
Layer
Primary owner
Verify
Sending identity
Sender and provider
SPF and DKIM results, plus DMARC alignment
Transport
Provider
TLS, acceptance, queues, and delivery events
Reputation
Shared
Complaints, bounces, deferrals, and blocks
Audience and consent
Sender
Signup source, suppressions, and inactivity policy
Message and stream
Sender
Purpose, sender, unsubscribe, HTML, and links
Monitoring
Shared
Provider logs, Postmaster Tools, and DMARC reports
How deliverability is measured: delivery rate vs inbox placement
Deliverability outcomes happen at two stages. Delivery rate reports whether the receiving server accepted the message. Inbox placement reports where an accepted message landed: the inbox, the spam folder, or a category such as Promotions. Track both, because a high acceptance rate can sit alongside spam placement. Read our tips to improve your inbox placement and why emails go to spam when placement slips. When either moves, inspect SMTP responses and what SMTP error codes mean, along with complaint data and provider logs, and run controlled inbox tests before changing anything. If failures happen at connection time, check your SMTP ports and protocols.
Email authentication: SPF, DKIM, and DMARC
SPF, DKIM, and DMARC let a receiver tie a message to the domain shown to the recipient. Google and Yahoo require bulk senders to authenticate with all three, keep complaint rates low, and offer one-click unsubscribe. Here is how SPF, DKIM, and DMARC work in Loops: SPF lists the systems allowed to send for an envelope domain, DKIM signs the message so a receiver can verify it was not altered, and DMARC checks that the SPF or DKIM domain aligns with the visible From domain. Start DMARC at p=none, read the aggregate reports until every legitimate sender aligns, then move to quarantine or reject. Generate the record with the DMARC record generator.
If you send through Loops, most of this is filled in for you. Loops generates the exact SPF, DKIM, and MX records for your domain and places its SPF record at an envelope subdomain such as envelope.yourdomain.com so it will not collide with an existing SPF record. You can also send from a subdomain instead of your root domain. Copy the records into your registrar once when you add your sending domain, then check your DNS records and click verify. Propagation time depends on DNS caching. Wait for domain verification before testing sends.
Sender reputation
Mailbox providers evaluate sending history at the domain and IP level. Complaints, hard bounces, invalid recipients, sudden volume changes, and repeated mail to inactive recipients all damage that history. Authentication establishes identity, but it does not create a good reputation on its own. Reputation is earned by consistent mail that recipients want. Learn how to build your sender reputation over time.
Warmup and sending volume
A new domain or dedicated IP has no history, so ramp it. Start with the recipients who most recently asked for the mail, raise volume in controlled steps, and slow down when deferrals, bounces, or complaints climb. A dedicated IP gives one sender full control of its IP history but needs enough steady mail to hold it, so a managed shared pool is often the better default for lower or uneven volume. There is no universal message count that makes a dedicated IP correct.
For specific cases, see sending to a large new audience, moving to a new sending domain, and sending from more than one domain.
List hygiene and consent
List quality starts with permission. Every address should have a clear source, a message type it can receive, and a suppression path. Purchased or scraped lists create complaint and spam-trap risk that authentication cannot repair. Use confirmed opt-in where a form is easy to abuse, reduce your product email bounce rate by suppressing hard bounces and complaints immediately, and keep your list clean by holding consent and unsubscribe state in one source of truth.
Engagement signals and content
Once identity and audience quality check out, look at the message itself. Complaints, unsubscribes, replies, clicks, and product activity reveal a mismatch between the audience and the send. Treat opens as directional, not exact. Here is why open rates are unreliable.
Use a recognizable From name, add a sending avatar so recipients know you, and a monitored reply address. Give marketing mail a visible unsubscribe link plus a one-click List-Unsubscribe header, and keep links on the sending brand, since shortened YouTube links flagged in Gmail can hurt placement. Test the final MIME message rather than the editor preview.
Monitoring and tools
What Loops handles, and what you own
Loops supplies sending-domain records, verifies the configured domain, and sends over managed infrastructure. It automatically suppresses hard bounces and complaints, and webhooks expose delivered, bounced, and complaint events for monitoring.
DNS ownership, DMARC policy, consent, segmentation, and message content stay with the sender.
Transactional email deliverability for SaaS
Keep account-critical messages separate from promotional campaigns in templates, triggers, monitoring, and rate controls. Verification links, password resets, receipts, billing notices, and security alerts should have one clear purpose and a recognizable sender.
Leave unrelated promotions out of required mail. Monitor transactional latency, bounce responses, and delivery events separately.
A campaign problem should not hide an authentication failure or a delayed account email.
If your recipients use shared mailboxes, follow the guide on delivering transactional email to group inboxes.
The deliverability checklist
Authentication
Sending from a dedicated subdomain, not the root domain
SPF published and passing
DKIM signing enabled and passing
DMARC published (none to quarantine to reject) with reporting on and alignment confirmed
Custom return-path aligned
BIMI only once DMARC is enforced
Reputation and warming
New domain or IP warmed gradually, most-engaged contacts first
Steady baseline cadence, such as a welcome workflow on every signup
Dedicated IP only if volume justifies it, otherwise a healthy shared pool
List and consent
Explicit opt-in only, no purchased or scraped lists
Confirmed opt-in for marketing signup forms that need protection against abuse
Inactivity policy based on sending cadence, clicks, replies, and product use, with opens treated as a limited signal
Hard bounces and complainers suppressed automatically
Engagement and content
Segmented, relevant sends
Recognizable From name and monitored reply address
One-click List-Unsubscribe header plus an obvious unsubscribe link
Complaint rate monitored in Google Postmaster Tools and kept below provider thresholds
Branded, understandable links and standards-compliant HTML with a plain-text alternative
Delivery events and inbox tests reviewed separately
Frequently asked questions
What is email deliverability?
What are the most important email deliverability best practices?
How do I improve email deliverability?
What is email authentication?
What is the difference between SPF, DKIM, and DMARC?
Do I need a dedicated IP for good deliverability?
What is a good spam complaint rate?
Does Loops handle deliverability for me?
How do I warm up a new domain or IP?
How do I monitor email deliverability?
