How do I check if Gmail is blocking me?

Send a test message to a Gmail address you own. Check the SMTP response in your ESP logs. 550-5.7.1 means hard block, 421-4.7.0 means temporary deferral. Check Google Postmaster Tools for domain reputation (Bad or Low indicates blocking risk). No public Gmail block list exists.

Does Gmail have a block list?

Gmail uses internal reputation systems, not a publicly queryable block list. They publish guidance through Google Postmaster Tools (showing your domain's reputation as Bad/Low/Medium/High) and via SMTP response codes when blocking. Gmail's filtering decisions are domain-and-IP-specific, not based on a public DNSBL.

Why does Gmail block my emails?

Common causes: failed SPF/DKIM/DMARC, high complaint rate (>0.3%), sending to spam traps, bulk send from new domain without warmup, low engagement history, sending IP shared with bad actors, or content matching phishing patterns. Diagnose via Postmaster Tools and SMTP response codes.

How long does Gmail block last?

Temporary blocks (421/4.7.0) clear in minutes to hours once sending behavior normalizes. Hard blocks (550/5.7.1) persist until the underlying issue is fixed and reputation recovers — typically 2-6 weeks of clean sending after remediation.

How do I get unblocked from Gmail?

There is no Gmail delisting form. Recovery requires fixing the cause (authentication, complaints, list hygiene), then sending consistent low-volume mail to engaged subscribers until Postmaster Tools reputation improves. Gmail's bulk sender contact form exists but only handles broader policy questions.

Gmail Block List Check: Are You Blocked, and What to Do

Gmail blocking your mail is a different problem than most other deliverability issues because Gmail does not maintain a public blocklist. There is no "Gmail blocklist check" you can run to see if you're listed. The signals come from SMTP response codes and Postmaster Tools — and many senders never look at either.

This guide walks through how to detect Gmail blocking, what's causing it, and how to recover. The principles apply to most modern ISPs (Outlook, Yahoo) but Gmail specifics matter because Gmail represents the largest single inbox provider.

How to detect Gmail is blocking you

Three signals:

1. SMTP response codes

When your mail server (or ESP) tries to deliver to Gmail, the server responds. Specific codes mean specific things:

Code	Meaning	Action
250 2.x.x OK	Accepted	Normal
421 4.7.0 IP not in whitelist	Temporary deferral, rate-limited	Slow down, retry
421 4.7.0 [TS01] Temporary block	Throttling	Reduce volume, investigate
421 4.7.0 Try again later	Generic deferral	Investigate reputation
550 5.7.1 Our system has detected...	Hard block, policy violation	Fix and rebuild
550 5.7.1 The IP you're using to send mail is not authorized	SPF/auth failure	Fix SPF
550 5.7.26 Unauthenticated email is not accepted from this domain	DKIM/DMARC issue	Fix DKIM and DMARC alignment
550 5.7.350 Remote server returned message	Bulk sender requirements not met	See Gmail/Yahoo bulk sender requirements

Pull these from your ESP's bounce logs or your own MTA logs (Postfix mail.log, Postal admin, etc.). If you see repeated 550 or 421 responses from Gmail, you're being blocked or throttled.

2. Google Postmaster Tools

Free, required reading for any sender mailing >10k Gmail addresses. Register at postmaster.google.com, verify your sending domain, and watch:

Domain reputation — Bad / Low / Medium / High
IP reputation — same scale, per sending IP
Spam rate — % of mail recipients marked as spam
Feedback loop — complaint signals
Authentication — SPF, DKIM, DMARC pass rates
Delivery errors — categorization of failures

If domain reputation is Bad or Low, Gmail is filtering or blocking most of your mail to spam. See Google Postmaster Tools guide.

3. Seed mailbox tests

Send a test message to a Gmail account you control. Check:

Did it arrive in Inbox, Promotions, or Spam?
What does the message header show in Authentication-Results?
Is the message threaded normally or flagged?

Use a Gmail account that does not have engagement history with your sender (a fresh account, not your work account that opens everything from you). This approximates a typical recipient experience.

Practitioner note: Most senders test deliverability to their own Gmail address, which is the worst test possible. Your personal Gmail has years of engagement history with your sending domain. It will land in inbox no matter what. Use fresh seed accounts, ideally several created at different times, with no prior interaction.

What's causing the block

Once you know Gmail is blocking, diagnose in order:

Authentication (5 min check)

Check SPF, DKIM, DMARC via Mail-Tester or MXToolbox. Gmail's bulk sender requirements (in force since 2024) reject mail from senders mailing 5,000+/day without all three. Common failures:

SPF has too many DNS lookups
DKIM not signing for the From domain
DMARC at p=none (not enforcing)
DKIM domain not aligned with From domain

See SPF, DKIM, DMARC.

Complaint rate (Postmaster Tools)

Gmail enforces a 0.3% complaint rate threshold for bulk senders. Above 0.1% you're at risk; above 0.3% you'll be filtered or blocked. The complaint rate in Postmaster Tools is the authoritative measure.

If complaints are high:

Audit signup sources — are people opted in clearly?
Check unsubscribe path — is it one-click and prominent?
Reduce frequency for promotional content
Sunset inactive subscribers (they're more likely to complain)

See Gmail complaint rate threshold and Gmail/Yahoo bulk sender requirements.

Sending volume and pattern

Sudden volume changes look like spammer behavior:

New domain sending at scale → warmup violation
Volume spike from established domain → suspicious
Multiple new domains pointing to similar campaigns → coordinated spam pattern

If you recently added new sending infrastructure or scaled volume, the fix is gradual warmup, not a single delisting request.

List quality

Sending to invalid, role, or trap addresses signals bad acquisition:

Bounce rate > 2% → throttling
Trap hits → reputation damage
Role address heavy → flag

Run hygiene through ZeroBounce or Kickbox. See list cleaning guide.

Practitioner note: Gmail throttles before it blocks. The progression looks like: normal delivery → 421 deferrals on a percentage of mail → 421 on all mail → 550 hard blocks → domain reputation drops to Bad in Postmaster Tools. Catching it at the 421 stage and fixing the cause prevents the hard block phase. Most senders only notice when they hit 550s, which means recovery is longer.

Recovery process

Once the cause is fixed:

Week 1:
- Confirm fix is deployed (authentication, hygiene, complaints)
- Drop sending volume to 30-50% of prior baseline
- Send only to highly engaged subscribers (opened in last 30 days)
- Monitor Postmaster Tools daily

Week 2-3:
- Gradually increase volume by 20-30% per week
- Maintain sending only to engaged segments
- Watch domain reputation trend in Postmaster Tools

Week 4-6:
- Resume normal sending if reputation has recovered to Medium or High
- Reintroduce lapsing subscribers cautiously
- Continue daily Postmaster Tools monitoring

Don't try to send to dormant subscribers during recovery. They are the segment most likely to complain or ignore, which depresses recovery.

Common mistakes during recovery

Sending more, hoping engagement will help — opposite effect; throttling gets worse
Switching domains without fixing root cause — new domain gets listed faster
Buying "delisting services" — Gmail has no delisting form for any service to use
Changing content (subject lines, copy) — irrelevant to reputation-based blocking
Submitting Gmail Bulk Sender contact form for "delisting" — that form is for policy questions, not block removal

The form at support.google.com/mail/contact/bulk_send_new is the bulk sender support contact. It does not unblock you. Recovery is mechanical and time-based.

For broader deliverability context see Gmail deliverability deep dive and why emails go to spam.

If you need help diagnosing Gmail blocking, running a structured recovery, or rebuilding domain reputation, book a consultation. I do Gmail recovery work for senders weekly and can speed the diagnostic.

Sources

v1.0 · May 2026