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SMTP error code · Gmail / Google Workspace

550 5.7.1: Gmail blocked likely unsolicited mail or low reputation

550 5.7.1 Permanent failure (5xx): the message bounced
By iBlockSpam Team Checked against sources 4 sources How we check our content
What it means

Gmail refused the message because it looks like unsolicited mail, or because the sending IP address or domain has a very low reputation.

What the bounce says
550 5.7.1 This message is likely unsolicited email. To reduce the amount of spam sent to Gmail, this message has been blocked.

Gmail's text (without its closing link), as listed in Google's SMTP errors reference. Gmail's replies can run over several lines; RFC 5321 says every line except the last starts with the code followed by a hyphen, so the same error can appear as 550-5.7.1.

What 550 5.7.1 means

Gmail uses 550 5.7.1 for many reasons, from admin policies to malformed headers. This entry covers the three reputation and spam texts in Google's reference:

  • "This message is likely unsolicited email."
  • "This message is likely suspicious due to the very low reputation of the sending IP address."
  • "This message is likely suspicious due to the very low reputation of the sending domain."

These are permanent rejections, so the messages bounced. Gmail decides based on the history of mail from your IP and domain: how recipients react, how much you send and how consistently, and whether you meet its sender guidelines (authentication, valid reverse DNS, TLS, low spam rates, easy unsubscribing for bulk mail). Gmail's guidelines ask senders to keep the spam rate reported in Postmaster Tools below 0.3%.

Reputation can't be repaired by a single setting. Fix the basics, find out why recipients don't want the mail, then send less, to engaged recipients, and let reputation recover over time. If the domain reputation is low and you never send bulk mail, check for a compromised mailbox or web form.

Likely causes

  • High spam complaint rates from Gmail users.
  • Sending to old, purchased or unconfirmed lists.
  • A compromised account or form sending spam from your IP or domain.
  • Missing authentication or reverse DNS, which makes the mail look less trustworthy.
  • Sudden volume spikes from an IP or domain with little history.

How to fix it

If you sent the message

  1. Make sure SPF, DKIM and DMARC pass and your sending IP has valid reverse DNS.
  2. Check for compromised accounts and forms; stop any spam at the source.
  3. Send only to recipients who asked for your mail; remove inactive and bouncing addresses.
  4. Add one-click unsubscribe to marketing mail and honor it quickly.
  5. Monitor spam rate and reputation in Google Postmaster Tools while you recover.

If you're the recipient or their admin

  1. Gmail users can mark a wanted sender's messages as not spam, but that doesn't override a 550 rejection at the server; the sender needs to fix their reputation.
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Frequently asked questions

How do I fix a low sending reputation with Gmail?

Meet Google's sender guidelines (authentication, reverse DNS, TLS, low spam rate), stop sending to people who didn't ask for your mail, and keep volume steady. Reputation recovers gradually as recipients engage with your mail instead of reporting it.

Is this the same as being on a blocklist?

Not exactly. Gmail rates IPs and domains itself. A public blocklist listing can come from the same underlying problem, though, so it's worth checking.

Sources

  1. Gmail SMTP errors and codes (Google Workspace Admin Help)
  2. Email sender guidelines (Gmail Help)
  3. RFC 3463: Enhanced Mail System Status Codes
  4. RFC 5321, section 4.2: SMTP replies (multiline reply format)

Provider messages are quoted as the provider publishes them. Servers can change their wording, so the bounce you received may differ slightly.

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