Email Deliverability Best Practices
Email deliverability is whether messages reach the intended inbox. Check authentication, sending reputation, audience consent, and message content when delivery or placement changes.
Start here
Read the guide on this page, or see what Loops runs on every send.
Authentication
SPF, DKIM, and DMARC tie your mail to your domain. Google and Yahoo require all three from bulk senders.
DMARC and DKIM setup
The records Loops creates for your domain and the ones you add.
SPF
Lists the servers allowed to send for your domain.
DKIM
Signs each message so receivers can check it came from your domain unchanged.
DMARC
Tells receivers how to handle mail that fails aligned SPF and DKIM.
BIMI
Shows your logo in supporting inboxes once DMARC is enforced.
Email authentication
How SPF, DKIM, and DMARC work together.
Free tools
Check records, build a policy, and review a draft in your browser. No signup.
Sending reputation and inbox placement
Complaints, bounces, and volume changes affect where providers place your mail.
Why are my emails going to spam?
Seven causes and how to check each one.
12 best email deliverability tools
Tools for authentication, reputation, placement tests, and list checks.
Sender reputation
How mailbox providers judge your domain and IP from past sends.
Inbox placement
Where an accepted message lands, from an inbox tab to spam.
IP warming
Raise volume on a new IP gradually so providers see wanted mail.
Email warmup
Ramp up a new sending domain, starting with engaged recipients.
Feedback loop
The signal a mailbox provider sends when someone reports spam.
Email blacklist
Blocklists of senders flagged for spam, and what a listing means.
Email list hygiene
Keep addresses and sending permissions current.
Spam trigger words
Phrases checkers flag, and why no universal list exists.
One-click unsubscribe
The RFC 8058 unsubscribe Google requires on bulk marketing mail.
SMTP and setup guides
Ports, protocols, and the server replies that explain a failed send.
SMTP error codes explained
What 421, 550, 554, and other server replies mean.
SMTP ports, IMAP vs POP3, and email verification
Ports 25, 587, and 465, TLS settings, and address checks.
Transactional email best practices
Keep account email reliable and separate from marketing.
Bounce rate
How to count failed deliveries consistently.
Hard bounce
A permanent failure. Stop sending to that address.
Soft bounce
A temporary failure. Follow the retry policy before you suppress.
The full guide
Check authentication first, then reputation, consent, and the message itself.
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. For the checks Loops runs for you, see how Loops handles deliverability.
Deliverability infrastructure map
Use provider logs for delivery failures and your own contact records for audience and consent checks.
Layer
Primary owner
Sending identity
Sender and provider
Transport
Provider
Reputation
Shared
Audience and consent
Sender
Message and stream
Sender
Monitoring
Shared
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.
If you send to Apple relay users, register your domain so you can reach Apple Hide My Email addresses.
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
Deliverability is a running measurement, not a one-time setup. Watch complaint rate, bounce responses, and delivery events per stream, and read the signals your mailbox providers publish. Gmail does not report spam complaints back to Loops, so set up Google Postmaster Tools to see how Gmail scores your sending.
See how Loops monitors your sends, and browse email deliverability tools to round out your stack.
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?
Email deliverability is whether a message reaches the intended inbox rather than being rejected or filtered to spam. Delivery rate only reports whether a receiving server accepted the message. Authentication, sending history, audience consent, complaints, bounces, and message construction all affect inbox placement.
What are the most important email deliverability best practices?
Authenticate the sending domain with SPF, DKIM, and DMARC. Send only expected mail, suppress hard bounces and complaints, increase volume gradually, and separate critical transactional mail from promotions. For subscribed marketing mail, support one-click unsubscribe. Monitor delivery events and provider feedback throughout.
How do I improve email deliverability?
Check SPF, DKIM, and DMARC alignment first. Then inspect bounce responses, deferrals, complaints, recent volume changes, audience source, and the final MIME message. Compare transactional and marketing streams separately, and change one variable at a time.
What is email authentication?
Email authentication connects a message to a domain. SPF authorizes sending systems for an envelope domain, DKIM signs the message, and DMARC checks alignment with the visible From domain and publishes a policy and reporting address.
What is the difference between SPF, DKIM, and DMARC?
SPF checks whether the sending system is authorized for an envelope domain. DKIM verifies a signature and signing domain. DMARC passes when aligned SPF or DKIM succeeds for the visible From domain. The published policy tells receivers how the domain owner wants failures handled, and can request authentication reports.
Do I need a dedicated IP for good deliverability?
Not automatically. A dedicated IP gives one sender control over its IP history, but it requires consistent volume, monitoring, and a warming plan. A managed shared pool can be a better default for lower or uneven volume.
What is a good spam complaint rate?
Google recommends keeping user-reported spam below 0.1% and avoiding 0.3% or higher. Yahoo requires bulk senders to remain below 0.3%. These providers calculate complaint rates differently, so use each provider’s dashboard and current guidance.
Does Loops handle deliverability for me?
Loops manages the sending service, provides and verifies sending-domain records, automatically suppresses hard bounces and complaints, and exposes delivery events. Your team still owns DNS policy, consent, segmentation, message classification, and the content sent to each recipient.
How do I warm up a new domain or IP?
Ramp gradually. Start with the recipients who most recently opted in, raise volume in controlled steps, and pull back whenever deferrals, bounces, or complaints rise. A steady baseline cadence, such as a welcome workflow on every signup, keeps the ramp consistent without manufacturing traffic.
How do I monitor email deliverability?
Track complaint rate, bounce responses, and delivery events per stream, and check the reports your providers publish. For Gmail specifically, use Google Postmaster Tools, because Gmail does not pass spam-complaint data back to sending platforms.
What's next
More on getting email delivered.