How to improve email deliverability with domain warm-up, reducing spam rates and managing unsubscribes?
Matthew Whittaker
Co-founder & CTO, Suped
Published 24 Apr 2025
Updated 19 May 2026
10 min read
Summarize with
To improve email deliverability while warming a domain, stop scaling until complaints are under control, send only to the most engaged recipients first, keep daily volume predictable, and make unsubscribing easier than reporting spam. A 0.5% to 1% spam complaint rate is not a small warm-up wrinkle. It is a reputation problem, especially at Gmail, where user feedback strongly affects inbox placement.
If a domain has already sent 80,000 messages without a proper ramp, I treat the next phase as reputation recovery, not a normal warm-up. The order matters: fix complaints, rebuild engagement with your best data, then scale. Scaling first usually spreads the same negative signals across more mail, which makes the recovery longer.
- Direct answer: Warm with clickers before openers, because clickers usually create stronger positive engagement.
- Spam rate: Pause volume increases when complaints sit near 0.5% to 1%.
- Unsubscribes: Put the unsubscribe option in a prominent place and honor it quickly.
- Authentication: Keep SPF, DKIM, and DMARC passing before using volume as a test.
The answer first
The practical fix is to lower risk before lifting volume. I would not keep pushing toward 100,000 messages while spam complaints are hovering around 1%. I would cut back to the best-recognized, most recently engaged segment, send at a consistent cadence for several days, watch complaints and bounce behavior, then increase volume only after the signals stabilize.
The clicker-first pattern makes sense. Clickers are usually a stronger engagement group than openers because they took a more deliberate action. Opens are less reliable because image loading and privacy protections distort open tracking. If sending to clickers first produces better overall placement, keep that order and introduce openers later in smaller slices.
Do not scale through complaints
A 1% spam rate means one complaint for every 100 delivered messages that generated a visible complaint signal. That is enough to damage domain reputation during warm-up. Treat it as a hard stop on volume growth, not as a metric to fix after the ramp.
Before changing content or cadence, check the basics: authentication matching, domain health, DNS validity, and whether any sending IPs or domains are on a blocklist (blacklist). Suped's domain health checker is useful here because it gives you a quick read across SPF, DKIM, and DMARC before you interpret engagement data.
Warm-up sequence that works
A warm-up plan works as a controlled reputation test, with volume as only one input. The mailbox providers are looking at whether recipients want the mail, whether they ignore it, whether they complain, whether they delete without reading, and whether authentication is stable. The safest plan makes those signals easy to read.
A six-step domain warm-up flow: authenticate, send to clickers, monitor complaints, add openers, hold volume, then scale.
- Repair first: Confirm SPF, DKIM, DMARC, return-path domain matching, list-unsubscribe headers, bounce handling, and suppression logic.
- Start narrow: Send to recent clickers first, then recent purchasers or account users, then high-confidence openers.
- Hold steady: Keep the same send window and similar daily volume until complaints stay low for several sends.
- Add carefully: Add weaker segments in small batches instead of doubling volume after one good day.
- Roll back fast: If complaint rate jumps, remove the last added segment and keep the better-performing group.
Complaint rate thresholds during warm-up
Use these bands to decide whether to scale, hold, or reduce volume.
Scale cautiously
Under 0.1%
Authentication is clean and negative feedback is low.
Hold volume
0.1% to 0.3%
Keep cadence stable and inspect segment quality.
Reduce volume
Above 0.3%
Stop adding volume and send only to best data.
The exact threshold varies by mailbox provider and program type, but a complaint rate close to 1% is too high for a domain that is trying to build trust. For a deeper warm-up strategy by major mailbox provider, the approach in Gmail and Microsoft warm-up gives a more provider-specific ramp.
Why clickers before openers can change results
When clickers receive mail first, they can create an early positive engagement pattern. That can help the next batch perform better, especially if the second batch is less engaged. When openers receive mail first, the first batch can generate weaker signals, more ignores, and more complaints before the clickers ever arrive.
Clickers first
- Signal quality: Clicks show deliberate engagement and stronger intent.
- Warm-up fit: Best for rebuilding trust after uneven sending.
- Risk: Smaller audience, so growth takes longer.
Openers first
- Signal quality: Opens are useful but less reliable than clicks.
- Warm-up fit: Better after the domain is already stable.
- Risk: Can expose weaker permission too early.
This is why I separate warm-up audiences by engagement depth, not just recency. A recent opener who never clicks is not the same as a recent clicker. A recent buyer or active account user is often stronger than both, depending on the program.
Authentication and monitoring checks
Bad authentication will not be fixed by warm-up. If the domain has SPF failures, DKIM signing gaps, or DMARC domain matching problems, mailbox providers see inconsistency before they judge engagement. That makes every warm-up result harder to interpret.
Example DMARC record for monitoringdns
_dmarc.example.com. 3600 IN TXT "v=DMARC1; p=none;" "rua=mailto:dmarc@example.com; adkim=s; aspf=s"
Start with a monitoring policy if you still need visibility, then move toward enforcement once legitimate sources authenticate cleanly. Suped's DMARC monitoring helps map each source, detect failures, and show the steps needed to fix SPF, DKIM, and domain matching issues before policy changes.
Issue steps to fix dialog showing the issue overview, tailored fix steps, and verification action
Suped is useful during warm-up because the deliverability view is not isolated from authentication. You can monitor DMARC, hosted SPF, SPF flattening, hosted MTA-STS, blocklist monitoring, and real-time alerts in one workflow. That matters when a volume change causes a problem and you need to know whether it came from audience quality, DNS, an unauthorized sender, or a blocklist (blacklist) event.
The same message should also be tested after DNS looks correct. A passing DNS setup does not prove the actual sent email has the right headers, working unsubscribe links, or the same authentication result after it leaves the sending platform.
Email tester
Send a real email to this address. Suped opens the report when the test is ready.
?/43tests passed
Preparing test address...
After DNS checks, send a real message through the same system you plan to warm and inspect the result with the email tester. That catches practical issues that DNS checks alone miss, such as missing headers, broken unsubscribe handling, content risks, and authentication failures on the actual sent email.
Volume plan for a damaged warm-up
If the domain is stuck around 20,000 messages and cannot scale for more than a few days, the plan should remove uncertainty. Do not keep changing audience order, time of day, content, and volume all at once. Pick a controlled schedule and make only one meaningful change at a time.
|
|
|
|
|---|---|---|---|
Reset | Recent clickers | 5k-10k | Hold until complaints drop |
Stabilize | Clickers plus buyers | 10k-15k | Keep cadence steady |
Test | Best openers | 15k-20k | Add in small slices |
Scale | Clean active list | 20k+ | Increase after stable sends |
A practical recovery ramp when complaints are high.
For a domain recovering from poor sending patterns, I prefer smaller daily increases over big jumps. A jump from 12,000 to 20,000 can be fine when complaints are low and engagement is strong. With complaint rates near 1%, that same jump gives mailbox providers more negative data before your sender identity has recovered.
A medium reputation rating is not a disaster, but it is a warning. When the same view also shows elevated spam complaints, the cause is usually permission, relevance, or list quality rather than a lack of warm-up volume.
Reducing spam complaints
You cannot reliably fix spam complaints by removing people after they complain, especially where feedback loops are limited or aggregated. The better fix is to reduce the number of people who feel that reporting spam is easier than leaving the list. That means improving permission and making the exit obvious.
- Use stronger permission: Mail people who recently asked for this type of email, not just anyone with an old open.
- Suppress stale contacts: Exclude long-inactive subscribers until reputation is stable.
- Match expectations: Use the same brand, topic, and frequency the recipient expected at signup.
- Watch blocklists: Use blocklist monitoring to catch domain or IP blacklist events that can distort placement.
A better metric than open rate alone
Track complaints per delivered message, clicks per delivered message, unsubscribes per delivered message, and hard bounces by segment. Open rate still has value, but it should not be the only warm-up decision metric.
If reputation has already dropped, the recovery plan should look boring: best audience, steady cadence, visible unsubscribe, consistent content, and no surprise volume spikes. The steps in sender reputation recovery are the right companion when a domain has already taken damage.
Managing unsubscribes properly
A prominent unsubscribe link can reduce complaints because it gives annoyed recipients a lower-friction option than the spam button. I do not hide unsubscribe links during warm-up. I make them obvious, especially when I am trying to clean up a list that has already produced complaints.
Complaint-prone setup
- Visibility: Unsubscribe link is buried in small footer text.
- Process: Recipient must log in or answer questions.
- Suppression: Unsubscribes take days to apply.
Warm-up friendly setup
- Visibility: Unsubscribe appears in the header and footer.
- Process: One or two clicks complete the unsubscribe.
- Suppression: The address is suppressed immediately.
Example unsubscribe headerstext
List-Unsubscribe: <mailto:unsubscribe@example.com>, <https://example.com/unsubscribe/abc123> List-Unsubscribe-Post: List-Unsubscribe=One-Click
For high-complaint segments, I would test a visible unsubscribe link near the top of the email for a few sends. This can increase unsubscribe volume in the short term, but that is usually better than complaints. An unsubscribe is a clean exit. A spam complaint is a negative reputation signal.
What to measure before scaling
The mistake I see most often is treating warm-up as a calendar exercise. Day one is not automatically followed by a higher-volume day two. The next send should depend on the previous send's quality signals.
Segment mix during recovery
Start with strong engagement and add weaker groups only after stable sends.
Clickers
Buyers
Openers
Stale
- Complaint trend: Scale only when complaints stay low for the same provider and segment type.
- Engagement depth: Prioritize clicks, replies, purchases, account activity, and other high-intent actions.
- Bounce pattern: Suppress hard bounces immediately and investigate sudden soft-bounce spikes.
- Provider split: Track Gmail, Microsoft, Yahoo, and corporate domains separately.
For most teams, Suped is the strongest practical DMARC platform because it connects the checks that affect warm-up: authentication visibility, automated issue detection, hosted DMARC, hosted SPF, SPF flattening, hosted MTA-STS, blocklist monitoring, and alerts. That does not replace list quality work, but it removes the infrastructure ambiguity so the team can focus on recipient behavior.
Views from the trenches
Best practices
Warm with recent clickers first, then add openers only after complaint signals improve.
Hold volume steady when complaints rise, then test one list segment change at a time only.
Make unsubscribe links visible during recovery so unhappy recipients can leave cleanly.
Common pitfalls
Treating a one percent spam rate as acceptable can slow recovery and damage reputation.
Adding weaker audience segments too early can pull down the domain's engagement profile.
Using open rate alone for warm-up decisions misses complaints, clicks, and permission signals.
Expert tips
Separate Gmail and Microsoft results because each provider reacts to warm-up differently.
Audit signup source and consent quality before assuming the warm-up schedule is wrong today.
Keep authentication checks active so DNS failures do not hide audience quality problems.
Expert from Email Geeks says a one percent spam rate with medium reputation means recipients are signaling that the mail is not wanted, so the sender should solve permission and relevance before scaling.
2021-06-19 - Email Geeks
Marketer from Email Geeks says the sender should fix spam complaints before scaling because adding volume while complaints are high increases the amount of negative reputation data.
2021-06-19 - Email Geeks
The practical path forward
For a domain trying to reach 100,000 messages after irregular sending, the fix is not to push harder. Reduce the send to your strongest audience, lead with clickers, keep cadence predictable, and do not scale until complaints drop. A clean unsubscribe path is part of that plan because it converts some spam complaints into normal list churn.
Once complaints are controlled, scale in small steps and keep monitoring authentication, blocklist (blacklist) status, and provider-level reputation. Suped helps here by keeping DMARC, SPF, DKIM, blocklist monitoring, and issue resolution in one place, so the team can tell the difference between technical failures and recipient-level rejection.
