Reputation, Blocklists and Warm-up

First 15 minutes

1. Read the current Google domain and IP reputation ratings for the affected stream.
2. Stop spam, malware, suspicious-domain, and unauthenticated sending behavior and begin reducing the user-reported spam rate.

Now

• Stop spam, malware, suspicious-domain, and unauthenticated behavior and reduce complaint-producing traffic.

Next 24 hours

• Send only wanted mail, confirm addresses, make unsubscribe easy, and consider removing inactive recipients.

Next 7 days

• Maintain consistent sending and gradual increases, reducing volume again if bounces or deferrals appear.

Technical checks

Verification criteria

• After corrective action for a high Gmail spam rate, allow up to seven days and confirm that the rate returns to a compliant level.
• Confirm SMTP error rates fall before increasing volume further.

Escalation criteria

• Escalate to a deliverability specialist if the corrected high Gmail spam rate has not returned to a compliant level after allowing up to seven days.

Prevention

• Send only to recipients who want the mail, confirm addresses, reconfirm interest periodically, make unsubscribe easy, and consider removing inactive recipients.
• Keep sending consistent and increase volume gradually, reducing it when bounces or deferrals begin.

Business impact

• Low reputation makes Gmail delivery to spam more likely, while bad reputation can make messages almost always spam-classified or rejected.

Provider notes

• Google bases domain and IP reputation on sending behavior and links worse ratings to spam classification or rejection.
• Google says a corrected high spam rate can take up to seven days to return to a compliant level.

Open questions

• No universal reputation-recovery duration applies across Gmail, Yahoo, Microsoft, private gateways, domains and IPs.
• The actual reputation driver cannot be selected without current complaint, bounce, authentication, traffic and recipient-engagement evidence.

First 15 minutes

1. Reduce volume to provider cohorts that are bouncing or deferring.
2. Capture rejection and temporary-failure rates, volumes, and reasons from Gmail Postmaster Tools and equivalent provider telemetry.
3. Check for infrastructure, header-structure, or bulk-format changes at the shared incident boundary.

Now

• Reduce affected Gmail-bound volume until the SMTP error rate decreases, then increase only slowly.

Next 24 hours

• Hold a steady warm-up volume at each mailbox provider and let each provider's delivery results control the next step.

Next 7 days

• Rebuild the ramp with low initial volume to engaged users, consistent sending, and continuous response and reputation monitoring.

Technical checks

Verification criteria

• At resumed low volume, sending remains consistent and SMTP responses and reputation are actively monitored before the next increase.
• Provider-by-provider delivery results remain stable at a steady volume before the next ramp step.
• For eligible Gmail traffic, Delivery Errors shows reduced rejected or temporarily failed volume and an understood reason mix.

Escalation criteria

• Escalate to the ESP or a deliverability specialist when errors persist at reduced volume or the provider reason cannot be isolated from message and telemetry evidence.

Prevention

• Ramp at a consistent rate to engaged users while monitoring provider responses and reputation throughout the warm-up.
• Introduce major infrastructure, header, and bulk-format changes as separately ramped segments.
• Keep warm-up volume steady across receiving providers and adjust each cohort from its own results.

Business impact

• Cross-provider rejection or temporary-failure volume can interrupt delivery across multiple customer cohorts while the ramp continues.

Provider notes

• Twilio SendGrid's dedicated-IP schedule extends beyond day 30 and is guidance for that product, not a universal cross-provider completion date.

Open questions

• The actual day-by-day volume, recipient-domain mix, SMTP responses, reputation data, engagement, content, list quality, and infrastructure changes are not provided, so day 30 cannot be assigned as the cause.
• Warmup schedules, thresholds, feedback, and tolerances differ by mailbox provider, ESP, IP type, domain history, recipient mix, and traffic quality.

First 15 minutes

1. Document the current amount sent, sending frequency, and available recipient feedback before selecting the next increment.
2. Capture Gmail SMTP responses, Postmaster Tools spam rate, and sending-domain reputation for the current ramp stage.

Now

• Reduce Gmail volume when messages begin bouncing or being deferred.

Next 24 hours

• Resume with low, consistent sending to engaged recipients only after the SMTP error rate decreases.

Next 7 days

• Increase gradually without bursts while preserving an engaged-recipient starting cohort.

Technical checks

Verification criteria

• The SMTP error rate decreases before the next volume increase is attempted.
• SMTP responses, Postmaster Tools spam rate, and domain reputation show no new deterioration at the current stage.

Escalation criteria

• If Gmail errors persist even at low volume, review individual messages and escalate the evidence to the deliverability or ESP owner before increasing again.

Prevention

• Begin future ramps with low, consistent volume to engaged recipients and increase slowly.
• Avoid sudden volume spikes when the domain lacks high-volume history.
• Make SMTP responses, spam rate, and domain reputation gates for each ramp increase.

Business impact

• A sudden increase without high-volume history can cause Gmail rate limiting or a domain-reputation drop.

Provider notes

• Google's pace factors and monitoring signals are guidance for delivery to personal Gmail accounts, not a universal new-domain quota.

Open questions

• There is no universal safe initial or daily message count; a defensible pace depends on provider response, audience quality, history, frequency, and feedback.

First 15 minutes

1. Confirm whether the account uses a Twilio SendGrid Free or Essentials shared IP pool, which does not require an individual IP warmup strategy.
2. Document how every warm-up recipient was sourced and whether that person signed up for the messages.
3. Baseline Gmail server responses, spam rate, and domain reputation before evaluating any ramp.

Now

• Stop any paid warm-up traffic that targets purchased or non-subscriber addresses.

Next 24 hours

• Replace synthetic traffic with low, consistent sending to engaged subscribers.

Next 7 days

• Increase real opted-in volume gradually while monitoring server responses, spam rate, and domain reputation.

Technical checks

Verification criteria

• The ramp uses engaged subscribers and low, consistent volume rather than manufactured recipient activity.
• Server responses, spam rate, and domain reputation are monitored before each gradual increase.

Escalation criteria

• Ask the ESP or deliverability owner to confirm whether the account uses shared or dedicated IPs before accepting a claim that individual IP warmup is required.

Prevention

• Prohibit purchased addresses and messages to people who did not sign up, including traffic labeled as warm-up.
• Use low, consistent, monitored sends to engaged subscribers for legitimate Gmail volume increases.

Business impact

• A gradual dedicated-IP warmup does not guarantee a perfect sending reputation.
• Messages to people who did not sign up can be reported as spam and can cause future messages to be classified as spam.

Provider notes

• SendGrid says gradual dedicated-IP warmup does not guarantee perfect reputation.
• SendGrid Free and Essentials customers on shared IP pools do not require an individual IP warmup strategy.

Open questions

• Primary sources do not establish a blanket return-on-investment verdict for every paid warm-up service; consulting-only services and synthetic-mail services are materially different.