Why does Google Postmaster Tools show delivery errors when emails are delivered?
Updated on 5 Oct 2026: We updated our advice on Gmail delivery errors with Deliverability analysis, clearer SMTP checks, and practical retry guidance.
Google Postmaster Tools can show delivery errors even when a sending platform later records the same messages as delivered because the Delivery Errors dashboard includes rejected messages and temporary failures. A temporary failure is an SMTP deferral, usually a 4xx response. If the sending system retries and Gmail later accepts the message, the platform records a successful SMTP delivery, while Postmaster Tools can retain the earlier deferral in its delivery error data.
The graph is not always saying "8% of the mail never arrived." It is saying that a percentage of SPF- or DKIM-authenticated messages was rejected or temporarily failed in Google's dashboard data. Treat that as a Gmail-side signal, then confirm the impact with complete SMTP response and retry logs. A 250 response from Gmail's receiving server after message DATA proves Gmail accepted the message, but it does not prove inbox placement or an open.
The practical rule: when Postmaster Tools shows delivery errors but the sending platform shows delivered, use SMTP logs to confirm whether Gmail ultimately accepted each message. Then use Postmaster Tools to investigate what Gmail rejected or deferred during the delivery path.
Common causes of conflicting delivery reports
The mismatch usually has one of these causes. A recovered temporary failure does not mean the message was permanently rejected, but repeated tempfails still need attention because they can slow delivery and lead to permanent failures.
- Tempfail counted: Gmail returns a 4xx response, the sender retries, and Gmail accepts the message later. Postmaster Tools can still show the temporary failure.
- Different datasets: The sending platform often records the final SMTP result. Postmaster Tools reports aggregated, delayed, privacy-filtered data for authenticated mail sent to personal Gmail accounts.
- Low-volume gaps: Google can omit dashboard data when volume is low, so a day or reason view can lack detail. Postmaster Tools uses UTC and typically updates within 24 hours, but updates can take longer.
- Forwarding effects: Google attempts to exclude forwarded messages, but some dashboards can still include them. A forwarding server can receive a failure that does not appear in the original sender's Gmail logs.
- Traffic outside your logs: Replayed messages with a valid DKIM signature can create authenticated failures associated with the domain even when first-party sends look clean.
Google's Postmaster Tools FAQ identifies delivery errors as a diagnostic signal. Its dashboard documentation specifies that the error rate covers messages that pass SPF or DKIM, including temporary failures. Google's delivery issue form also covers rejected messages and temporary delivery failures. "Accepted after retry" and "temporarily failed" can both be true.
Postmaster Tools v2 launched in 2024. Google's interface retirement notice still postpones retirement of the legacy web interface and gives no replacement date. Delivery Errors is available in v2; Domain and IP Reputation are the exceptions Google plans to retire. Use Compliance status, Spam rate, authentication data, and SMTP logs for current investigations.
Google Postmaster Tools delivery error chart with an 8% spike and no detail rows.
Why delivered email can still show an error
SMTP delivery is a sequence of attempts. If Gmail replies with a temporary failure, the sending server or email platform should queue the message and retry. When a later attempt succeeds, many dashboards show only Gmail's final 250 acceptance after message DATA. Google Postmaster Tools can still show the earlier temporary failure in its aggregate delivery error data.
Illustrative retry patterntext
10:02:11 UTC Queue q123: Gmail returns 421 4.7.0 Try again later 10:07:18 UTC Queue q123: Sender retries the queued message 10:07:19 UTC Queue q123: Gmail returns 250 2.0.0 after DATA Final platform status: delivered
That pattern is common during domain or IP warmup, after sudden volume increases, and when Gmail throttles bursty traffic. A warmup that moves too fast can create tempfails without producing final bounces. Stop sending briefly when rate-limit errors appear, then resume at a slower, constant rate and use exponential backoff for retries. Track queue age and retry exhaustion, because a recovered deferral still delays delivery and an expired queue can produce a final bounce.
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|---|---|---|
Delivery Errors graph | Gmail saw authenticated failures | SMTP logs |
No detail | Reason data is missing; the cause is unconfirmed | UTC date, volume, and later updates |
Delivered | Platform reports acceptance; verify Gmail's response | Receiving server and retry history |
4xx | Temporary failure | Full response and retry timing |
5xx | Permanent failure | Full response text |
How to read conflicting delivery views
Do not ignore repeated tempfails because the final platform status says delivered. Rate-limit tempfails require slower traffic. Continuing at the same rate can cause longer queues and further rejections.
Match dashboard reasons to SMTP evidence
The Delivery Errors category is a starting point, not a replacement for the full SMTP response. Gmail began ramping up enforcement of its sender requirements in November 2025, including temporary and permanent rejections for non-compliant traffic, as described in its sender guidelines FAQ.
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|---|---|---|
Rate limit exceeded | Burst rate, warmup pace, retry timing | 421 4.7.28; confirm the full response |
DMARC policy or authentication requirement | SPF, DKIM, DMARC policy, and From domain alignment | 4.7.26 or 5.7.26 (DMARC); 4.7.27 or 5.7.27 (SPF); 4.7.30 or 5.7.30 (DKIM); 4.7.32 or 5.7.32 (From domain); 4.7.40 or 5.7.40 (missing DMARC policy) |
Bad or missing PTR record | Matching forward and reverse DNS | 4.7.23 or 5.7.25 |
Missing TLS | TLS use on the connection to Gmail | 4.7.29 or 5.7.29 |
Suspected spam or low reputation | Consent, complaints, sending pattern, and content | 4.7.0, 4.7.28, 5.7.1, or 5.7.28 |
Unsupported attachment | Attachment type and message format | 5xx response with the rejection reason |
Public RBL listing | Domain or IP blocklist (blacklist) source | Named domain or IP and full rejection text |
Postmaster Tools reasons and related Gmail SMTP errors
Do not infer the fix from the first digit alone. Preserve the enhanced status code, full response text, sending IP, timestamp, recipient domain, and queue ID. That evidence separates a sender-requirement rejection from an ordinary recipient or system error. Use Google's SMTP error reference to interpret the complete response.
For a 4xx response, keep the message queued and retry with exponential backoff. For a 5xx response, stop retrying that failed delivery unchanged and fix the stated cause before sending again. Suppress a confirmed nonexistent recipient, such as 550 5.1.1; an authentication rejection does not mean the address is invalid.
Which delivery data to trust
Start with the source that answers the exact question. For "did Gmail ultimately accept this message?", use the final SMTP response. For "did Gmail throttle or reject authenticated traffic?", use Postmaster Tools as an aggregate diagnostic signal. Neither source alone proves inbox placement.
Your sending logs
- Attempt result: Shows whether Gmail accepted, deferred, or rejected each message attempt.
- Best detail: Gives timestamps, SMTP response codes, queue retries, and final status.
- Main gap: Gmail's 250 acceptance after DATA does not reveal whether it placed the message in the inbox or spam.
Postmaster Tools
- Gmail signal: Shows Gmail's aggregate view of authenticated mail to personal Gmail users.
- Best use: Highlights throttling and current compliance or authentication trends.
- Main gap: Data is delayed, privacy-filtered, and sometimes lacks reason-level detail.
The Postmaster Tools percentage and a sending platform's hard bounce rate measure different outcomes. For example, if logs show 99.9% final Gmail acceptance and Postmaster Tools shows an 8% delivery error spike, look for Gmail 4xx responses first. Do not assume 8% of recipients missed the email unless final logs or bounce data support that conclusion.
Google Postmaster Tools delivery error troubleshooting using SMTP logs and 4xx or 5xx responses.
Check Gmail's diagnosis with Deliverability analysis
Open Compliance status in Postmaster Tools v2 and review Deliverability analysis. Google's dashboard guidance describes recommendations for insufficient sending volume, delivery failures, excessive spam reports, recipient interaction, and sender-requirement compliance.
Use the recommendation to prioritize the matching SMTP errors and affected sending source. Treat it as a domain diagnostic; it does not prove that an individual message reached the inbox.
Compliance status uses a rolling average and includes subdomain traffic in the primary domain's status. Google advises allowing up to seven days for fixes to appear. Keep checking SMTP logs during that delay and respond to ongoing rejections.
Checks to run before changing sending
Do not change DNS, pause a sender indefinitely, or blame an email platform based on the Postmaster Tools graph alone. Run a short sequence that separates display gaps, temporary throttling, authentication problems, and real reputation damage.
- Pull logs: Export delivery attempts to @gmail.com and @googlemail.com for the same UTC date and authentication domain shown in Postmaster Tools. Exclude Google Workspace custom-domain recipients. Group retries by queue ID and follow messages across UTC midnight to their final result.
- Compare volume: Look for a sudden send increase, uneven campaign timing, new IP traffic, or a warmup step that was too aggressive. On shared IPs, ask the sending provider about IP-level throttling affecting other customers.
- Verify authentication: Check SPF, DKIM, and DMARC results on production messages, including From domain alignment. Use Suped's domain health check to inspect the DNS records.
- Check sender health: Review Compliance status, Spam rate, unsubscribe handling, and relevant blocklist (blacklist) signals. Google's sender FAQ recommends staying below 0.1% user-reported spam and avoiding 0.3% or higher.
- Test the path: Send a real message through the production path and review the headers with Suped's email tester before making broad changes.
Email tester
Send a real email to this address. Suped shows a results button when the test is ready.
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Suped is our DMARC reporting and email authentication platform. Its reports help trace a Gmail authentication symptom to a sending source or DNS record, while its blocklist monitoring supplies domain and IP blacklist evidence.
Issues page showing top issues, verified sources, unverified sources, and authentication pass rates
When managing multiple domains in Suped, investigate each domain's sources and issues separately. SMTP logs remain the evidence for Gmail acceptance; DMARC aggregate reports do not record every retry or prove inbox placement.
When the graph deserves action
A one-day delivery error spike with no matching final bounces differs from a worsening sender problem. Base the decision on persistence, SMTP code class, and related Gmail signals.
Operational triage examples
Practical examples for prioritizing delivery error investigations by SMTP evidence and queue impact.
Watch
Isolated spike
Recovered deferrals with stable queues and no authentication or complaint change.
Investigate
Recurring deferrals
Recurring deferrals or queue growth, even when messages ultimately arrive.
Act
Immediate
Confirmed policy rejections or authentication failures; messages exceed delivery deadlines.
Act quickly when delivery errors coincide with a Compliance status problem, a complaint spike, or increased DMARC failures. Suped's DMARC monitoring connects failures to sending sources. Use its blocklist monitoring when the rejection text names a domain or IP blacklist. A listing alone does not establish that Gmail used that list.
Investigate DKIM replay when Gmail reports failures missing from first-party logs. Reused messages can retain a valid DKIM signature without a stolen key, as described in RFC 6376. Use separate keys per sender to help isolate the source. Revoking a key can also affect queued legitimate messages. Stronger DMARC enforcement alone does not stop a replay that still passes DMARC.
Escalate unresolved Gmail delivery issues
Compare the Delivery Errors chart with related Postmaster Tools views. If the Authentication dashboard also looks wrong, the guide on SPF and DKIM rates covers that dataset. If Postmaster Tools shows no rows or visible detail, the guide on missing GPT data explains low-volume and visibility gaps.
For escalation, keep the evidence tight: affected domain, UTC date, accepted count, temporary failure count, permanent failure count, sample SMTP responses, authentication results, and any Compliance status change. A verified domain owner can use Report delivery issue after confirming the domain meets Gmail's sender guidelines, the message passes SPF and DKIM, and the From header domain matches the selected domain. For an accepted message, copy the headers through Gmail's Show original view and use Get message info for me in the delivery issue report to populate its details. Track the submission under Reported issues.
Views from the trenches
Best practices
Compare GPT spikes with raw SMTP logs before changing DNS or stopping campaigns.
Separate 4xx tempfails from 5xx rejections so the response fits the failure type.
Track warmup pace by Gmail domain data, not only by total campaign delivery rate.
Common pitfalls
Treating the GPT percentage as a hard bounce rate causes unnecessary panic for teams.
Ignoring retry history hides tempfail patterns that final delivered status masks.
Overlooking forwarded mail can misattribute downstream failures to otherwise clean sends.
Expert tips
Use unique DKIM keys per sender so replay or source issues are easier to isolate.
Reduce broad SPF includes because excessive authorization increases domain exposure risk.
Pause briefly after repeated tempfails, then resume at a slower, steadier send rate.
Marketer view
Marketer from Email Geeks says Postmaster Tools delivery errors are often tempfails, even when the final delivery attempt succeeds after retry.
2024-02-28 - Email Geeks
Expert view
Expert from Email Geeks says sender logs should be treated as the final delivery record, with Postmaster Tools used as a Gmail-side signal.
2024-02-28 - Email Geeks
What to do next
If Google Postmaster Tools shows delivery errors while the sending platform shows delivered messages, first test whether the graph reflects temporary failures or a dataset mismatch. Check every SMTP attempt, not only the final status. If the logs contain repeated rate-limit 4xx responses, stop briefly, resume at a slower constant rate, and review the next available daily report while tracking queue delays.
If the logs show permanent policy rejections, authentication failures, or persistent delays for time-sensitive messages, correct the stated cause before resuming affected traffic. Suped's DMARC reports help identify authentication problems at the sending source.
