Gmail 550 5.7.1: low domain reputation.

Gmail blocked the message because the sending domain has low reputation.

How to fix 550 5.7.1.

Retrying or final
Final
A 5xx reply. The server will not accept this message. Resending it unchanged fails again.
Who is at fault
Sender
Your authentication, reputation, content, or sending pace.
Severity
ErrorDomain Reputation
Permanent550 5.7.1

New domains, poor engagement, or recent spam complaints trigger Gmail’s domain reputation filters. The message is rejected outright.

Next steps

  1. 1Warm new domains slowly, starting with long-term engaged users.
  2. 2Monitor domain reputation charts inside Google Postmaster Tools.
  3. 3Align SPF, DKIM, and DMARC so authentication is airtight.
  4. 4Segment aggressive promotions onto hardened domains or subdomains.
Gmail documentationEvery raw SMTP 550 reply

The same code at other providers.

Providers word the same code differently. Their fixes differ too.

550 5.7.1 [CS01]Apple Mail (iCloud)Local policy blockFinal
550 5.7.1Apple Mail (iCloud)Spamhaus SBL blockFinal
550 5.7.1 LPN007_517Laposte.netDMARC policy rejectFinal
550 5.7.1 LPN007_518Laposte.netContent policy blockFinal
550 5.7.1SFRSpam policy rejectionFinal
550 5.7.1OrangeSpam policy rejectionFinal

More Gmail codes.

Full Gmail playbook

Other Gmail fixes

550 5.7.1Message flagged as spamFinal
550-5.1.1Recipient address does not existFinal
550 5.1.0User unknownFinal
550 5.2.1Mailbox disabledFinal
452 4.2.2Mailbox fullRetrying
421 4.7.0Temporary system problemRetrying

In the glossary

Bounce (Hard)Hard bounce is when an email cannot be delivered because the address is invalid or blocked. It is a permanent failure and the address should be removed from your list.
Suppression ListA suppression list is the place your email tool keeps addresses that should not receive messages. It is a permanent "do not send" list that helps you avoid emailing people who have opted out or caused issues in the past.
List HygieneList hygiene is the practice of cleaning your email list by removing bad or inactive addresses. It keeps your list focused on people who still want your emails.
Bounce RateBounce rate is the percentage of emails that could not be delivered to recipients. It shows how many addresses are invalid or blocked compared to the total you tried to send.

Browse all raw Google replies →

More references.

SMTP field manual.

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