Guide
Gmail 550 5.7.1: what each version means and what to do
550 5.7.1 is a family of refusals, not a single error. The sentence after the code tells you which one you have.
Short answer
550 5.7.1 means the receiving server refused the email permanently. Read the text after the code: it might be the recipient's own policy [1], a judgement that the email is "likely unsolicited" [2], a low domain reputation [3] or a rate limit [4]. Do not resend the same email. Stop sending to that recipient, and if several arrive in a row, stop sending new emails altogether until you know why.
Find the sentence after the code
The bounce arrives from "Mail Delivery Subsystem". Under the code there is a sentence, and the sentence is the diagnosis. Two more things matter: who refused it (a Google server, or the recipient's own server, which may use the same code with its own text) and how many (one bounce is about one recipient; several in a day are about you).
The versions you are likely to meet
| What the bounce says | What it means | What to do |
|---|---|---|
| "The user or domain that you are sending to (or from) has a policy that prohibits the email that you sent." [1] | The recipient's organisation blocks this email, often all mail from outside, or from your domain. | Do not retry. Remove the address. If it was a real contact, reach them another way. |
| "This message is likely unsolicited email." [2] | Gmail judged the email to be spam. | Stop new first emails for the day. Look at the email itself: links, attachments, a pitch with no reason to write to this person. |
| "This message is likely suspicious due to the very low reputation of the sending domain." [3] | Your domain's reputation with Gmail is poor, usually from spam reports or bounces. | Stop sending cold email from this domain. Check Postmaster Tools. Rebuild slowly with people who expect your email. |
| "This email has been rate limited." [4] | Too much mail, too fast. | Pause, then send more slowly and spread through the day. |
| 550 5.4.5 "Daily user sending limit exceeded." [5] | Not 5.7.1, but often confused with it: you hit your mailbox's daily limit. | Wait. Sending works again within 24 hours [6]. |
| 5.7.26, not authenticated | The email failed SPF and DKIM checks. Google says such messages "might be marked as spam or rejected with a 5.7.26 error" [7]. | Fix SPF, DKIM and DMARC on your domain before sending again. |
Why one bounce is not the problem, and five are
A single 5.7.1 from a company's own server is about that company. A run of them from Gmail is about you, and it compounds: Google warns that "If messages from your domain are frequently reported as spam, future messages from you are more likely to be marked as spam" [8]. Its own advice when bounces start is to "reduce the sending volume until the SMTP error rate decreases" [9]. Keep sending through a wave of bounces and you also risk the mailbox: many undelivered emails can stop you sending for 24 hours [10].
A short checklist
- Read the sentence, not just the code.
- Never resend the bounced email unchanged.
- Remove addresses that bounced for policy or non-existence; do not write to them again.
- Three bounces in a short run: stop new first emails and look before continuing.
- Check SPF, DKIM and DMARC once, so 5.7.26 is never the reason.
How Honest Intros handles bounces
Honest Intros reads bounces in the threads it started and recognises them by their sender and wording. A bounce stops the follow-ups to that person. Three bounces or policy blocks among a mailbox's last thirty first emails pause new first emails until a person has looked; sending then resumes at half the daily cap.
Questions
What does 550 5.7.1 mean in Gmail?
It is a permanent refusal. The sentence after the code says why: the recipient's policy, a spam judgement, a low reputation or a rate limit, among others.
Should I resend an email that bounced with 550 5.7.1?
No. A 5xx code is permanent. Resending the same email to the same address only adds another bounce to your record.
Is 550 5.7.1 my fault or the recipient's?
Read who sent the bounce and what it says. A policy refusal from the recipient's own server is about them; a spam or reputation refusal from Gmail is about your email or your domain.
How do I fix a low domain reputation in Gmail?
Stop sending cold email from the domain, check Postmaster Tools, and rebuild slowly by writing only to people who expect your email. There is no quick reset.
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