Why are my emails going to spam after migrating to a new domain and ESP, and what steps can I take to improve inbox placement?
Updated on 10 Oct 2026: We updated this guide with suppression checks, current sender requirements, and practical warmup steps.
Spam placement after a new domain and ESP migration often points to an unfamiliar sending identity or mistakes in authentication and list handling. Changes to the From domain, DKIM signing domain, tracking links, IP pool, and sending pattern can make Gmail, Outlook, and corporate filters treat the mail as unproven, even when the brand is legitimate.
Start by verifying authentication, preserving suppression rules, warming the new domain with engaged subscribers, and monitoring complaints alongside DMARC results. Treat seed-list results as directional evidence. Poor search rankings do not directly make email land in spam, but insecure links, suspicious redirects, malware, or a poor sending-domain reputation can contribute to filtering.
Separate the problem into identity, infrastructure, audience, and content. That keeps the work practical: confirm the domain can authenticate, prove the new ESP is sending correctly, send first to people who actually engage, then remove the content and link patterns that make filters cautious.
Why a new domain and ESP can trigger spam filtering
A domain that has never sent mail has no positive sending history. That does not mean it has a bad reputation. It means mailbox providers have little evidence that recipients want the mail. When that new domain also starts sending through a new ESP, filters see several changes at once: changes to headers, DKIM signing, bounce handling, tracking links, IP addresses, and sometimes HTML.
Delivery rate and inbox placement measure different outcomes. A delivered message was accepted by the receiving server, but it can still land in spam or another filtered folder. Use provider-level engagement, complaints, bounces, and placement tests together instead of treating the ESP's delivered count as proof of inbox placement. Gmail's Promotions tab counts as inbox delivery. See Gmail's inbox categories.
- New identity: The visible From domain, DKIM domain, return-path domain, and link tracking domain can all look new to filters.
- New infrastructure: A new ESP can change IP pools, mail transfer patterns, bounce domains, and header structure.
- Weak early engagement: Sending first to inactive contacts creates fewer useful recipient signals and increases complaint risk.
- Content carryover: Similar spam placement on both systems points to shared audience or message issues as well as infrastructure.
- Testing noise: Seed-list tests can swing widely because inboxing is not a single domain-wide decision.
A cold domain can show spam placement in tests before it has sent real mail. That is not proof of permanent damage. Validate authentication and compare test results with real subscriber outcomes before increasing volume.
ESP migration troubleshooting with authentication checks, domain warmup, content review, engagement, and monitoring.
What changed during the migration
Treat an ESP migration as a change to the sending identity. Even when the sender name and logo stay the same, the technical identity behind the mail often changes.
Before migration
- Known patterns: Mailbox providers had history for the old domain, old ESP, and old sending rhythm.
- Existing recipients: Engagement signals were tied to the previous sending identity and message stream.
- Known issues: Complaints, stale contacts, or weak content can already be present. Compare opens cautiously because ESPs measure automated activity differently.
After migration
- New signals: The new domain and ESP need fresh evidence that recipients want the mail.
- Fresh risk: Authentication mistakes, tracking changes, and warmup gaps have immediate impact.
- Same audience: A poor or inactive list still hurts, even when the domain is new.
A cousin domain is a separate registered domain, rather than a subdomain of the original domain. Reputation does not transfer automatically to it, but changing domains does not erase the effects of shared IPs or a poor list. A subdomain also does not guarantee reputation isolation. If the same people ignored, deleted, or complained about earlier messages, the new domain will face the same recipient behavior.
With a shared IP pool, other senders affect the IP reputation. A new dedicated IP needs its own gradual volume ramp; dedicated infrastructure does not automatically improve inbox placement. Ask the ESP which IPs carry your traffic and who manages reverse DNS (PTR) records. Google's sender guidelines explain shared-IP reputation.
If both old and new systems show spam placement, focus on the shared factors first: the list, content, offer, sending cadence, and sender reputation signals that surround the brand. Then verify the new ESP setup so a fix in content is not hidden by an authentication failure.
Preserve suppression lists and consent during migration
An ESP migration can accidentally reactivate people who unsubscribed, complained, or hard bounced on the old platform. Import suppression lists before enabling campaigns and automation; an active-contact export alone is incomplete.
- Transfer unsubscribed addresses, spam-complaint suppressions, and hard-bounce records. Preserve list-specific opt-outs and subscription preferences.
- Keep each contact's consent source and timestamp. A new domain or ESP does not create fresh permission to send marketing email.
- Sync new opt-outs and complaints across both ESPs during the overlap. Stop old automations and queued campaigns at handover to prevent duplicate sends.
- Exclude stale, purchased, and scraped lists. Abandoned addresses can become recycled spam traps, and address verification does not establish consent or guarantee a trap-free list.
Compare suppression counts and spot-check previously suppressed contacts before the first campaign. Confirm that signup forms and unsubscribe events reach the new ESP. Microsoft's migration guidance explicitly includes suppression-data transfer.
Check authentication before judging placement
Authentication does not guarantee inbox placement, but broken authentication can disrupt a migration. Configure SPF for the ESP's actual return-path domain, enable custom DKIM signing, and verify DMARC with reporting. DMARC passes when at least one passing SPF or DKIM domain meets DMARC alignment with the visible From domain; bulk-sender rules also require both SPF and DKIM to pass. Start with a domain health check, then inspect a received message's Authentication-Results header.
Illustrative DNS authentication patterndns
example.com. TXT "v=spf1 include:esp.example -all" selector1._domainkey.example.com. TXT "v=DKIM1; k=rsa; p=..." _dmarc.example.com. TXT "v=DMARC1; p=none; rua=mailto:dmarc@example.com"
The SPF include and DKIM key above are placeholders, not deployable records. Use the ESP's supplied values and a working reporting address. The p=none example requests monitoring; keep an existing quarantine or reject policy when legitimate mail passes.
- SPF pass: Publish one SPF record at the envelope From (return-path) domain. Its evaluation must stay within SPF's 10-term lookup limit, including nested includes.
- DKIM pass: Enable the ESP's custom signing and check the DKIM d= domain in received headers. Keep old selectors published while queued or delayed mail is still arriving.
- DMARC alignment: At least one passing SPF or DKIM identifier must meet the DMARC domain-matching rules. Relaxed alignment permits the same organizational domain; strict alignment requires an exact domain match.
- Reporting: Aggregate reports show sending sources and authentication results. They do not measure inbox placement, clicks, or recipient engagement.
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What's your domain score?
Deep-scan SPF, DKIM & DMARC records for email deliverability and security issues.
Suped is our DMARC reporting and email authentication platform. Its DMARC monitoring groups authentication results by sending source, so you can distinguish failures from the new ESP, an old platform still sending, or a forgotten sender using the domain.
Suped DMARC dashboard showing email volume, authentication health, and source breakdown
Meet current bulk-sender requirements
A migration is a good time to check current mailbox-provider requirements, not only whether DNS records exist. Noncompliant mail can be filtered or rejected, and successful authentication still does not guarantee inbox placement.
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About 5,000 or more messages in 24 hours to personal Gmail accounts, counted across a primary domain and its subdomains. | SPF and DKIM must pass; DMARC with at least p=none must pass. Also check TLS, valid forward and reverse DNS, RFC 5322 formatting, spam rates below 0.3%, and one-click unsubscribe plus a visible body link for marketing and subscribed mail. | |
Bulk senders, with no public fixed-volume threshold. | SPF and DKIM, passing DMARC with at least p=none, valid forward and reverse DNS, RFC-compliant mail, complaint rates below 0.3%, and one-click plus a visible body unsubscribe link for marketing and subscribed mail. Honor opt-outs within two days. | |
Domains sending at least 5,000 messages a day to Microsoft consumer services, including Outlook.com and Hotmail. | SPF and DKIM must both pass, and DMARC must pass with at least p=none. Noncompliant mail is subject to rejection with SMTP error 550 5.7.515. |
Bulk-sender checks that matter after a domain or ESP migration.
Google's bulk-sender FAQ states that bulk-sender classification is permanent once assigned. Sending less later does not remove those obligations.
For Gmail, implement RFC 8058 one-click unsubscribe using both headers below. A body link alone does not meet that requirement. Yahoo also accepts a functioning mailto unsubscribe header, but the POST method meets Gmail's requirement too. Keep the visible body link and honor requests within two days; Yahoo requires this timing and Google recommends it.
RFC 8058 one-click unsubscribe headerstext
List-Unsubscribe: <https://domain.com/unsub/opaquepart> List-Unsubscribe-Post: List-Unsubscribe=One-Click
Under RFC 8058, both unsubscribe headers must be covered by a valid DKIM signature. Test the HTTPS POST endpoint through the new ESP and confirm that it removes the subscription without a login or confirmation step.
Do not wait for a rejection to fix compliance. Verify the exact From domain, DKIM d= domain, return-path domain, and unsubscribe headers in a message sent through the new ESP before increasing volume.
Warm the domain with real recipient signals
Warmup means gradually increasing real, wanted email volume while checking recipient response. Start with subscribers who recently clicked, purchased, replied, logged in, or otherwise showed clear intent. Treat opens as supporting evidence because privacy-related automated opens can inflate the metric. Suppress prior complainers, hard bounces, and clearly inactive contacts before the first send.
Gmail user-reported spam rate during warmup
Google recommends keeping its daily user-reported spam rate below 0.10% and avoiding 0.30% or higher. These are Gmail-specific guideposts, not a universal recovery score.
Target
Below 0.10%
Consider increases only when other provider signals remain stable.
Caution
0.10% to below 0.30%
Pause increases and review list source and content.
Reduce volume
0.30% and above
Reduce volume and send only to strongest engagement.
Use Google's complaint-rate guidance alongside each provider's own metric definitions. Google's spam-rate definition uses messages delivered to engaged inbox recipients, so a low rate can coexist with heavy spam filtering. Missing data at low volume also does not prove good reputation.
There is no universal day-by-day warmup schedule. Send at a consistent rate and increase gradually only when provider-specific signals stay stable. Slow down if deferrals, bounces, or complaints increase. Google's sending-volume guidance recommends starting with low volume to engaged users.
- Initial batch: Send only to recently engaged subscribers and keep the sender name recognizable.
- Increase volume: Expand gradually only if provider-level complaints, bounces, SMTP responses, and engagement remain stable.
- Expand the audience: Add moderately engaged subscribers after stable results, while keeping inactive segments suppressed.
- Normal cadence: Resume planned volume after sustained stability. Include both ESPs' sends in the total while they overlap.
Do not warm a new domain by sending generic test messages with subjects like "test" and empty body copy. Those messages lack normal engagement context and can be filtered differently than real campaigns. Base warmup on legitimate subscriber mail and avoid exchanges that manufacture engagement.
Check templates and tracking links after migration
When the old and new ESP show similar spam placement, review shared content and audience factors. Check link destinations, redirect chains, HTML validity, and unsubscribe handling against what subscribers expect. No single word or fixed image-to-text ratio determines inbox placement.
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HTTP links | Unencrypted destinations and HTTPS errors need review; HTTP alone does not establish the spam cause. | Use working HTTPS links and validate every destination. |
Redirects | Shared tracking domains or broken redirect chains introduce additional domains to inspect. | Configure a branded tracking domain, verify HTTPS, and test each redirect. |
Images | Large embedded images increase message size; remotely hosted images affect download weight. | Resize and compress assets, keep essential information in text, and add useful alt text. |
Copy | Misleading subject lines or broken merge tags undermine recipient trust. | Keep the sender name recognizable and the copy consistent with the subscription. |
Unsubscribe | Broken opt-outs push recipients toward spam complaints. | Test the body link and required one-click headers after migration. |
Content checks that commonly matter after a migration.
Long URLs are not automatically spammy. The bigger issue is how those URLs behave. A long URL on your own HTTPS domain is usually better than a public shortener because public shorteners are shared by many unrelated senders. Use readable anchor text, keep the destination on your own domain where possible, and avoid chains of redirects.
Compressing remotely hosted images reduces download weight; it does not shorten their URLs or reduce the HTML markup. If a diagnostic tool complains about URL length, do not treat image compression as the fix. Check whether the link is HTTP, whether it redirects through an untrusted domain, and whether the destination page is clean. Check HTML size separately, including the markup added by tracking.
Email tester
Send a real email to this address. Suped shows a results button when the test is ready.
?/43tests passed
Send a real campaign-style message to an email tester after every template change. A single isolated score matters less than repeatable findings: failed DKIM, missing List-Unsubscribe, large HTML, broken images, or suspicious redirect chains.
Read seed-list tests carefully
Seed-list tests are useful, but they are not a perfect model of your audience. Inbox placement is not one global result for a domain. It varies by mailbox provider, corporate filtering stack, recipient history, engagement, folder behavior, and local policy. A high spam percentage in a seed test does not establish the percentage for your real subscriber list.
Useful signals
- Provider pattern: Repeated Gmail-only or Outlook-only issues help narrow the investigation.
- Authentication result: Header-level failures in test mail are worth fixing immediately.
- Content warning: Repeated link, image, or HTML issues point to template work.
Weak signals
- Single run: One test can swing because seed inboxes have little recipient history.
- B2B gap: Seed coverage varies; it cannot reproduce every corporate filter or recipient policy.
- Fake content: A blank test message does not behave like a real newsletter.
If real clicks, replies, and conversions are stable, the test can be overstating the problem. Use opens as supporting evidence because automated privacy activity can distort them. Compare engagement definitions across ESPs before concluding that a change in reported rates is a placement problem. If real engagement is low, complaint rate rises, or provider data shows poor reputation, the seed-list warning deserves more weight. For a deeper diagnostic sequence, use a migration-specific checklist like deliverability drops and compare it against your actual recipient metrics.
Check domain and IP reputation after migration
Poor SEO is rarely the direct reason email goes to spam. Mailbox providers care about recipient behavior, authentication, sending patterns, complaints, bounces, and message safety. Search visibility is a different system. The overlap is domain trust: if the website has malware, deceptive redirects, broken HTTPS, or risky pages, that can hurt.
Also check whether the sending domain, tracking domain, or sending IP appears on a blocklist or blacklist. A listing is not always the cause, but it changes the investigation. Suped's blocklist monitoring keeps domain and IP checks next to DMARC and source-level authentication data.
Blocklist checker
Check your domain or IP against 144 blocklists.
An unknown reputation rating or missing data can reflect too little sending history. A low rating is a warning to investigate, rather than a reason to assume the domain simply lacks history. Recipient complaints or a relevant blacklist (blocklist) listing also call for closer investigation. Check the exact listed domain or IP and fix the cause before requesting removal.
Do not move full volume onto a new domain just because its DNS records exist. Verify DMARC in received headers, then judge recipient interest and sender reputation before scaling.
Use a controlled recovery plan
Use a written rollout that says who gets mail, how much volume moves each day, which metrics decide whether to increase, and what changes if Gmail or Outlook starts filtering heavily. Separate temporary SMTP 4xx deferrals or throttling from permanent 5xx rejections, and keep the full response text to identify authentication, reputation, or recipient-address failures.
- Freeze risky sends: Pause inactive segments, purchased contacts, cold outreach, and high-frequency campaigns.
- Fix DNS: Verify SPF, DKIM, and DMARC in received headers, then check bounce and tracking domains. Ask the ESP to confirm reverse DNS for its sending IPs.
- Clean content: Fix insecure or broken links, public shorteners, oversized templates, broken HTML, and weak unsubscribe placement.
- Start narrow: Send to recent engagers first, preferably recipients who know the brand.
- Watch providers: Track Gmail, Outlook, Yahoo, and corporate domains separately. Reduce traffic to an affected provider when deferrals or spam complaints rise.
- Advance slowly: Increase only after complaints, bounces, clicks, replies, and DMARC pass rates stay healthy.
Suped's source-level DMARC reports and issue steps help confirm that the new ESP is authenticating correctly. Use its alerts to catch authentication failures during the rollout, and compare those findings with engagement and SMTP results in your ESP.
Issue steps to fix dialog showing the issue overview, tailored fix steps, and verification action
Compare ESP and domain changes against the actual sending headers and traffic records. For dedicated infrastructure, account for the separate reputation of new IPs and domains.
