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Gmail 550 5.7.1: very low sender reputation

550 5.7.1Blocked for very low sending IP or domain reputationPermanent: retrying will not helpFrom Gmail and Google Workspace

Typical wording
550-5.7.1 [203.0.113.50] Our system has detected that this message is likely suspicious due to the very low reputation of the sending IP address. To best protect our users from spam, the message has been blocked. - gsmtp

What it means

This rejection is aimed at the sender rather than the content. Gmail has recorded enough bad history for the IP address, and sometimes the domain, that it refuses mail outright. The wording typically mentions “very low reputation” and names either the sending IP address or the domain.

It often follows a run of 4.7.28 or 4.7.0 deferrals that were ignored. While the deferrals are temporary, this 550 response is final for each message, and every new message from the same source tends to receive it until reputation recovers.

Likely causes

  • Sustained high spam complaint rates from Gmail users over several days or weeks.
  • Spam traps hit because of old, scraped, or purchased address lists.
  • A brand new domain or IP that sent heavy volume immediately with no history to balance it.
  • Malware or a compromised mailbox on your network sending large amounts of spam.

How to fix it

  1. Open Google Postmaster Tools for the domain and check the IP and domain reputation charts. “Bad” confirms this cause.
  2. Find and stop any abusive traffic, rotate credentials of compromised accounts, and close open relays or forms.
  3. Send only to recently engaged recipients and confirmed opt-ins while you recover.
  4. Keep authentication complete (aligned SPF, DKIM, and DMARC) so good mail is credited to your domain.
  5. Raise volume gradually; reputation rebuilds over weeks, not hours.

Checks that apply

  • Blacklist Check Finds listings on major DNSBLs that usually accompany a collapse in Gmail reputation.
  • Domain Health Grades the domain end to end so you know authentication is not adding to the problem.
  • ASN Lookup Shows who owns the sending IP range, useful if a shared hosting network is the real source of the reputation.
See the example diagnosed

The classification runs without network lookups and we never store your paste.

FAQ

Should I just move to a new IP?
Rarely helpful. Gmail also tracks domain reputation, and a fresh IP with no history and bad habits will sink in the same way.
How long until Gmail accepts mail again?
It depends on how bad the history is. Senders who clean lists and stop abuse typically see improvement over two to six weeks.

Google Postmaster Tools Google email sender guidelines

All 191 bounce codes