# Why is Gmail blocking emails from my domain, and how do I fix it?

URL: https://iblockspam.com/blog/gmail-blocking-emails-from-my-domain
Last updated: 2026-11-03
Published: 2026-11-03
Topic: Running email day to day
Author: iBlockSpam Team

> Why Gmail rejects, rate-limits or junks mail from your domain, what each 5.7.x and 4.7.x code means, how to fix it and when to use Google's sender contact form.

## Short answer

Gmail blocks mail from a domain that fails SPF, DKIM or DMARC, lacks reverse DNS or TLS, draws a user-reported spam rate near 0.3%, or has a poor sending reputation. Read the bounce code, fix that requirement, slow your volume and check Postmaster Tools. Compliant bulk senders can then request mitigation through Google's sender contact form.

When Gmail refuses your mail, it bounces with a code that names the problem, and Google says it has been ramping up enforcement of its sender rules since November 2025. This guide shows how to tell a block from spam-folder placement, what Gmail's main codes mean, the order to fix things in, and how to ask Google for help, as documented at the time of writing (November 2026). It applies whether you send from Microsoft 365, Google Workspace, your own server or an email platform.

## Why is Gmail blocking emails from my domain?

Gmail blocks mail when it can't verify that your domain sent it or doesn't trust the sender. Google's [email sender guidelines](https://support.google.com/mail/answer/81126) say that if you don't meet them, "your email might not be delivered as expected, or might be marked as spam." The usual causes are:

- **Authentication.** Every sender must set up SPF or DKIM. Bulk senders, those sending more than 5,000 messages a day to Gmail accounts, also need DMARC and a From domain aligned with SPF or DKIM.
- **Infrastructure.** Google requires a TLS connection and "valid forward and reverse DNS records, also referred to as PTR records" for sending domains or IPs.
- **Spam reports.** Google asks senders to keep the spam rate reported in Postmaster Tools "below 0.10% and avoid ever reaching a spam rate of 0.30% or higher."
- **Reputation and behavior.** Sudden volume spikes, mail to people who didn't sign up, and shared IPs used by other bad senders.

Authentication terms are explained in [SPF vs DKIM vs DMARC](https://iblockspam.com/blog/spf-vs-dkim-vs-dmarc). Google's [FAQ](https://support.google.com/mail/answer/14229414) says that "starting November 2025, Gmail is ramping up its enforcement on non-compliant traffic," with temporary and permanent rejections. Domains that got away with weak setups before are now seeing bounces.

## Is Gmail blocking my mail or sending it to spam?

These are different problems. A **block** is a bounce: Gmail refuses the message during delivery and your server receives an error code. **Spam placement** means Gmail accepted the message but filtered it, so there's no bounce and the recipient finds it in Spam.

| Symptom | What's happening | Where to look |
|---|---|---|
| Bounce with 550 or 554 | Permanent rejection | The bounce text and code |
| Bounce with 421 or 451, or mail delayed for hours | Temporary deferral or rate limit | Your server's queue and logs |
| No bounce, recipient finds it in Spam | Accepted and filtered | Authentication results in the message headers, Postmaster Tools spam rate |
| No bounce, recipient can't find it anywhere | Possibly blocked by the recipient's own settings or admin | Ask the recipient; check their filters and blocked senders |

If your mail is going to spam rather than bouncing, start with [why emails go to spam](https://iblockspam.com/blog/why-are-my-emails-going-to-spam). The rest of this guide focuses on rejections and rate limits.

## What do Gmail's rejection codes mean?

Gmail's reply codes name the requirement that failed. The quoted wording is from Google's [SMTP errors and codes](https://knowledge.workspace.google.com/admin/support/troubleshooting/gmail-smtp-errors-and-codes) page.

| Code | Gmail says | Most likely fix | Reference |
|---|---|---|---|
| 550 5.7.26 | "This email has been blocked because the sender is unauthenticated." Other variants cite an SPF hard fail or your DMARC policy | Make SPF or DKIM pass and align | [550 5.7.26](https://iblockspam.com/smtp-errors/550-5-7-26) |
| 550 5.7.27 | "This message was blocked because it didn't pass SPF authentication." | Add the sending service to SPF | [550 5.7.27](https://iblockspam.com/smtp-errors/550-5-7-27) |
| 550 5.7.30 | "This message was blocked because it didn't pass DKIM authentication." | Turn on or repair DKIM | [550 5.7.30](https://iblockspam.com/smtp-errors/550-5-7-30) |
| 550 5.7.40 | "Your message was blocked because the sending domain doesn't have a DMARC record" | Publish DMARC, at least p=none | [550 5.7.40](https://iblockspam.com/smtp-errors/550-5-7-40) |
| 421 4.7.32 | Rate limited because the From header "isn't aligned" | Align SPF or DKIM with the From domain | [421 4.7.32](https://iblockspam.com/smtp-errors/421-4-7-32) |
| 550 5.7.25 | "The sending IP address doesn't have a PTR record" | Set reverse DNS | [550 5.7.25](https://iblockspam.com/smtp-errors/550-5-7-25) |
| 550 5.7.29 | "It wasn't sent over a TLS connection." | Enable TLS on the sending server | [550 5.7.29](https://iblockspam.com/smtp-errors/550-5-7-29) |
| 421 4.7.28 | "Gmail has detected an unusual rate of email." | Slow down; check reputation | [421 4.7.28](https://iblockspam.com/smtp-errors/421-4-7-28) |
| 550 5.7.1 | "This message is likely unsolicited email," or the sending domain has "very low reputation" | Fix list practices and reputation | [550 5.7.1 unsolicited](https://iblockspam.com/smtp-errors/550-5-7-1-gmail-unsolicited) |
| 550 5.7.28 | "There is an unusual rate of unsolicited email originating from your IP address." | Find the abusive stream or compromised account | [550 5.7.28](https://iblockspam.com/smtp-errors/550-5-7-28) |

A typical rejection, as it appears in a bounce message (the domain is an example):

```
550-5.7.26 Unauthenticated email from example.com is not accepted due to domain's DMARC policy.
```

Codes in the **4.7.x** range are temporary. Gmail is telling you to fix something and retry, and it may turn into a permanent 5.7.x rejection if nothing changes. Our [SMTP Error Code Lookup](https://iblockspam.com/tools/smtp-error-codes) decodes the rest.

## How do I fix Gmail blocking my domain?

Work through these steps in order. Authentication fixes solve most 5.7.2x and 5.7.30 errors on their own.

1. **Save the full bounce.** Copy the code, the text, the sending IP and the time. Note which sending service sent the message: your mailbox provider, a CRM, a newsletter platform or a website.
2. **Check one real message.** Send from the affected service to a personal Gmail account, open it, click **More** (three dots) and **Show original**. Google's [full-headers help](https://support.google.com/mail/answer/29436) gives this path (Reply, then **More**, then **Show original**), and the summary at the top of that view shows SPF, DKIM and DMARC as PASS or FAIL. Or send a message to our [Deliverability Test](https://iblockspam.com/tools/deliverability-test).
3. **Fix SPF.** Make sure the service that bounced is in your SPF record and that you have exactly one record. See [SPF record syntax](https://iblockspam.com/blog/spf-record-syntax-examples) and check yours with the [SPF Checker](https://iblockspam.com/tools/spf-checker).
4. **Fix DKIM.** Turn on DKIM signing with your own domain for every service. Google requires keys "of 1024 bits or longer" for personal Gmail. Our [DKIM setup guide](https://iblockspam.com/blog/dkim-setup-microsoft-365-google-workspace) covers Microsoft 365 and Google Workspace.
5. **Publish DMARC and check alignment.** Even `p=none` satisfies Google's bulk requirement. Alignment means the domain in your From address matches the domain that passed SPF or DKIM; see [DMARC alignment](https://iblockspam.com/blog/dmarc-alignment-relaxed-vs-strict). The [DMARC Checker](https://iblockspam.com/tools/dmarc-checker) confirms your record.
6. **Check reverse DNS and TLS** if you run your own server. Use the [PTR Lookup](https://iblockspam.com/tools/ptr-lookup) and our guide to [STARTTLS](https://iblockspam.com/blog/starttls-email-encryption-in-transit).
7. **Rule out compromise.** A sudden 550 5.7.28 or 5.7.1 from an office server often means a hacked account or contact form sending spam. Check the [signs of a compromised account](https://iblockspam.com/blog/signs-email-account-compromised).
8. **Reduce volume and clean the list.** Google's advice is to "start with a low sending volume to engaged users, and slowly increase the volume over time," and not to send "to people who didn't sign up." Remove bounced addresses.
9. **Watch Postmaster Tools for a week.** Then request mitigation if the problem persists.

### Is it my domain or my IP?

Gmail judges both. If you send from Microsoft 365, Google Workspace or an email platform, your mail leaves from shared IPs managed by the provider. Google says "the activity of any senders using a shared IP address affects the reputation of all senders for that shared IP address." Your part is your domain: authentication, list quality and spam reports. If you run your own server, the IP's reverse DNS, blocklist status and history are your responsibility too. Check it with the [Blacklist Checker](https://iblockspam.com/tools/blacklist-checker).

One code points at routing rather than reputation. "The IP you're using to send email is not authorized to send email directly to our servers" usually means mail is leaving from a network that shouldn't deliver directly, such as a home connection. See [550 5.7.1 IP not authorized](https://iblockspam.com/smtp-errors/550-5-7-1-gmail-ip-not-authorized) and send through your provider's [smart host](https://iblockspam.com/blog/what-is-a-smart-host-smtp-relay) instead.

## How do I see what Gmail sees with Postmaster Tools?

Google Postmaster Tools is Google's free dashboard for senders to personal Gmail accounts. Once you verify your domain, it shows your compliance with the sender guidelines, your user-reported spam rate, authentication results and delivery errors. Our [Postmaster Tools guide](https://iblockspam.com/blog/google-postmaster-tools-guide) explains setup and each dashboard, so here are only the parts that matter during a block:

- **Compliance status** shows which requirement is marked "Needs work." It uses a rolling average, so fixes can take days to show.
- **Spam rate** tells you whether you're above Google's limits. Our [spam complaint rate guide](https://iblockspam.com/blog/spam-complaint-rate-explained) covers how to bring it down.
- **Delivery errors** shows the share of your mail Gmail rejected or deferred, which helps you confirm a fix is working.

Postmaster Tools needs enough volume to show data. A small business sending a few dozen messages a day to Gmail may see little there, and should rely on bounces and test messages instead.

## How do I ask Google to unblock my domain?

Google doesn't offer an unblock button. It offers **mitigation**: a review for senders who follow the rules but are still filtered. The [sender contact form](https://support.google.com/mail/contact/gmail_bulk_sender_escalation) says it's for "senders who follow the Sender Guidelines, and still experience an excessive rate of spam classification along with a proportionally low volume of user spam reports."

Eligibility has firm limits. Google's FAQ says "only bulk senders that meet all the requirements" can get mitigation, that bulk senders with a user-reported spam rate above 0.3% are ineligible, and that they become eligible again "when their spam rates remain below 0.3% for 7 consecutive days."

When you submit:

1. Fix everything in the steps above first. The sender guidelines warn that senders who don't follow best practices "may not be considered for deliverability mitigations."
2. Prefer the **Report delivery issues** form inside Postmaster Tools. The contact form itself recommends it "so that you can track the status and resolution of your issue."
3. Choose the issue type: messages classified as spam or phishing, or SMTP temp-fails or rejects.
4. Paste full headers from a recent message. The form asks for one "less than 12 days old."
5. Describe what you fixed and when, and include the exact error codes.

If you send from a personal Gmail account rather than your own domain, the form directs you to Gmail's help on bounced or rejected email instead. Google's [troubleshooter for senders](https://support.google.com/mail/answer/80086) walks through other cases.

## What if one Gmail user or Workspace organization blocks me?

If only one recipient is affected, the problem is probably their mailbox. Gmail's [spam help](https://support.google.com/mail/answer/1366858) says a user can open **Spam**, select your message and click **Not spam**, after which "future emails from that sender won't go to Spam." Adding you to their contacts also helps. Google warns that if the user has blocked you, your messages keep going to Spam even after they're removed from it.

Google Workspace organizations are different. Google's FAQ says the sender guidelines "don't apply to messages sent to Google Workspace accounts." Those organizations' admins can still block or quarantine your domain with their own settings, such as a [blocked senders list](https://iblockspam.com/blog/google-workspace-blocked-senders-list) or the [Gmail spam settings](https://iblockspam.com/blog/gmail-spam-settings-google-workspace). Ask the recipient's IT team to check their policies, and send them the bounce text. If you're that admin and want to allow a sender, see [how to whitelist a sender](https://iblockspam.com/blog/whitelist-sender-microsoft-365-google-workspace).

## Next steps

- Send a test to the [Deliverability Test](https://iblockspam.com/tools/deliverability-test) and fix any SPF, DKIM or DMARC failure first.
- Check your domain against Google's rules with the [Bulk Sender Requirements Checker](https://iblockspam.com/tools/bulk-sender-checker).
- Look up each bounce in the [SMTP Error Code Lookup](https://iblockspam.com/tools/smtp-error-codes).
- Set up [Postmaster Tools](https://iblockspam.com/blog/google-postmaster-tools-guide) and watch spam rate and compliance for 7 days before asking for mitigation.
- If reputation is the problem, follow the [sender reputation recovery plan](https://iblockspam.com/blog/sender-reputation-recovery-plan); if Yahoo is also refusing you, see [Yahoo Mail blocking emails](https://iblockspam.com/blog/yahoo-mail-blocking-emails).
- Keep the DNS records that fixed it from drifting: iBlockSpam's [domain monitoring](https://iblockspam.com/features/domain-monitoring) alerts you when SPF or DMARC change.

Browse more guides on [running email day to day](https://iblockspam.com/blog/topic/operations).

## Frequently asked questions

### Why did Gmail suddenly start rejecting mail from my domain?

Usually something changed: a DNS edit broke SPF or DKIM, a new sending service went live without authentication, volume jumped, a campaign drew spam reports, or a hacked mailbox started sending spam. Google has also tightened enforcement since November 2025, so mail that used to be delivered despite missing authentication can now be refused. Read the bounce code first.

### Does Gmail's 550 5.7.26 error mean my domain is blacklisted?

No. 550 5.7.26 means the message failed authentication: it was unauthenticated, failed an SPF hard fail, or failed your own domain's DMARC policy. It's a setup problem, not a reputation listing. Fix SPF and DKIM so at least one passes and aligns with your From domain, then resend.

### Can I ask Google to unblock my domain?

You can ask for mitigation, but only if you already follow Google's sender guidelines. Bulk senders above a 0.3% user-reported spam rate are ineligible until their rate stays below 0.3% for 7 consecutive days. Use the sender contact form, or the Report delivery issues form in Postmaster Tools, which Google recommends so you can track the request.

### Do Gmail's sender rules apply when I email Google Workspace users?

No. Google's FAQ says the sender guidelines don't apply to messages sent to Google Workspace accounts; requirements and enforcement apply only to personal Gmail accounts. Mail to Workspace organizations still goes through Gmail's spam filtering and through that organization's own admin settings, which can block or quarantine your domain.

### Why does Gmail rate-limit my email with 421 4.7.28?

Gmail says it has detected an unusual rate of email and has temporarily rate limited it to protect users from spam. It usually follows a sudden volume increase or a reputation drop. Let your server retry, lower the sending rate, send to engaged recipients first, and check Postmaster Tools for spam rate and authentication problems.

## Sources

- [Gmail Help: Email sender guidelines](https://support.google.com/mail/answer/81126)
- [Gmail Help: Email sender guidelines FAQ](https://support.google.com/mail/answer/14229414)
- [Google Workspace Admin Help: Gmail SMTP errors and codes](https://knowledge.workspace.google.com/admin/support/troubleshooting/gmail-smtp-errors-and-codes)
- [Gmail Help: Sender contact form](https://support.google.com/mail/contact/gmail_bulk_sender_escalation)
- [Gmail Help: Troubleshooting for senders with email delivery issues](https://support.google.com/mail/answer/80086)
- [Gmail Help: Mark or unmark Spam in Gmail](https://support.google.com/mail/answer/1366858)

## Free tools for this guide

- [Email Deliverability Test](https://iblockspam.com/tools/deliverability-test): Send one email and see its SPF, DKIM and DMARC results, reverse DNS, blocklists, TLS and spam verdict.
- [Bulk Sender Requirements Checker](https://iblockspam.com/tools/bulk-sender-checker): Check your domain against the Gmail, Yahoo and Outlook.com bulk sender rules that DNS can show, with a checklist per provider.
- [DMARC Checker](https://iblockspam.com/tools/dmarc-checker): Check your policy, reporting and the safe path from p=none to reject.
- [Reverse DNS (PTR) Lookup](https://iblockspam.com/tools/ptr-lookup): Check PTR records, forward-confirmed reverse DNS and generic-looking host names.

---

Source: iBlockSpam, https://iblockspam.com/blog/gmail-blocking-emails-from-my-domain (this is a Markdown copy; the HTML page is canonical). Quote with attribution and a link. Site index for AI assistants: https://iblockspam.com/llms.txt