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Error code wiki · 108 codes

Gmail and Google Workspace SMTP error codes

Google runs Gmail and the mail service of Google Workspace, so its servers receive mail for gmail.com, googlemail.com and every business domain whose mail is hosted on Workspace.

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Permanent failures (5xx)

69 codes

The receiving server refused the message for good. Your server will not try again, and the message comes back to you as a bounce.

  1. 5.7.32From domain not aligned, blocked.Gmail blocked your message because the domain in its From address aligns with neither the domain that passed SPF nor the domain that signed DKIM.Permanent
  2. 501 5.5.2Cannot decode response.Gmail could not decode a reply your client sent, which during SMTP sign-in usually means a malformed base64 string in the AUTH exchange.Permanent
  3. 501 5.5.4Invalid or empty HELO name.Your client greeted Gmail with an empty or invalid name in its EHLO or HELO command, so Gmail refused it and closed the connection.Permanent
  4. 501 5.7.11No parameters allowed.Gmail refused a command because your client added parameters that the command does not take, most likely to STARTTLS.Permanent
  5. 502 5.5.1Command not recognized.Gmail does not know, or does not support, an SMTP command your client sent, and after too many of them it ends the session.Permanent
  6. 503 5.5.1Command sent out of sequence.Your client sent Gmail an SMTP command at the wrong point in the conversation, such as the message before any recipient, so Gmail refused it.Permanent
  7. 503 5.5.1EHLO or HELO missing.Your client started sending mail commands to Gmail without first greeting it with EHLO or HELO, which SMTP requires.Permanent
  8. 503 5.5.1DATA sent after BDAT.Your client began sending the message in BDAT chunks and then switched to DATA in the same transaction, which the CHUNKING extension does not allow.Permanent
  9. 503 5.7.0No identity changes permitted.Your client tried to authenticate again in an SMTP session where Gmail had already accepted a sign-in.Permanent
  10. 504 5.7.4Unrecognized authentication type.Your client asked Gmail to sign in with an authentication mechanism that Gmail does not offer, so the sign-in was refused.Permanent
  11. 504 5.7.4XOAUTH no longer supported.Your client tried to sign in with XOAUTH, Google's old OAuth 1.0 mechanism, which Gmail has retired in favor of XOAUTH2.Permanent
  12. 523 5.7.10Commands pipelined after STARTTLS.Your client sent more commands straight after STARTTLS without waiting for the TLS handshake, which Gmail treats as a protocol violation.Permanent
  13. 530 5.7.0Authentication required.Your client tried to send through a Google SMTP server that needs a signed-in account, without signing in first.Permanent
  14. 530 5.7.0STARTTLS required first.Gmail requires your client to switch the connection to TLS with STARTTLS before it signs in or sends mail, and your client did not.Permanent
  15. 534 5.7.9App password required.The account uses 2-Step Verification, so Google will not accept its normal password from your mail client and asks for an app password instead.Permanent
  16. 534 5.7.9Sign in with a web browser first.Google refused your client's SMTP sign-in and wants the account owner to sign in through a web browser first, where Google can run its checks.Permanent
  17. 534 5.7.14Sign in through a web browser first.Google refused your client's SMTP sign-in and wants the account owner to sign in through a web browser before the client tries again.Permanent
  18. 535 5.7.8Username and password not accepted.Google rejected the user name and password your client used to sign in to its SMTP server, so it will not send mail for it.Permanent
  19. 550 5.1.1Recipient address does not exist.There is no Gmail or Google Workspace account at the address you wrote to, so Gmail rejected the message permanently.Permanent
  20. 550 5.2.1Recipient account is inactive.The Gmail account you wrote to is disabled or inactive, so it cannot receive mail, and Gmail rejected your message permanently.Permanent
  21. 550 5.2.1Recipient receiving too much mail.Gmail permanently rejected your message because the recipient's account is receiving mail faster than Gmail lets it accept.Permanent
  22. 550 5.4.5Daily sending limit reached.The Gmail or Workspace account sending this message has reached its daily sending limit, so Google is refusing further mail from it for now.Permanent
  23. 550 5.4.5Daily relay limit reached for a user.A Workspace user has sent more mail through smtp-relay.gmail.com today than the SMTP relay service allows for one user.Permanent
  24. 550 5.5.3Too many recipients for this sender.Gmail refused further recipients because this sender has gone over the number of recipients Gmail will accept from it.Permanent
  25. 550 5.7.0Relay denied: sender not registered.Google's SMTP relay refused your mail because it comes from an IP or domain that is not registered in your Google Workspace account's relay settings.Permanent
  26. 550 5.7.0Relay account suspended for abuse.Google has temporarily suspended the account behind your relayed mail from sending, because it detected abuse such as spam from it.Permanent
  27. 550 5.7.0Email sending denied.Google refused to send this mail through its servers for your account, and its reply refers you to the SMTP relay error documentation.Permanent
  28. 550 5.7.1Blocked by a domain policy.A rule set by the recipient's or the sender's Google Workspace admin blocks this message, so Gmail rejected it under that policy.Permanent
  29. 550 5.7.1Relay IP does not match the sending domain.Google's SMTP relay knows your IP, but the mail's sending domain is not one that IP is registered to relay for in your Workspace account.Permanent
  30. 550 5.7.1Blocked as likely spam.Gmail's filters judged this message likely to be spam and rejected it outright, instead of delivering it to the spam folder.Permanent
  31. 550 5.7.1IPv6 sender without PTR or authentication.Gmail rejected mail that arrived over IPv6 because the sending address lacks a matching PTR record, or the message failed authentication.Permanent
  32. 550 5.7.1Blocked for low IP reputation.Gmail permanently rejected the message because the IP it came from has a very low reputation with Gmail.Permanent
  33. 550 5.7.1Blocked for low domain reputation.Gmail permanently rejected the message because the domain it comes from has a very low reputation with Gmail.Permanent
  34. 550 5.7.1Missing or invalid From header.Gmail rejected the message because it has no From header, or the From header does not contain a valid email address.Permanent
  35. 550 5.7.1Missing Message-ID header.Gmail rejected the message because it has no Message-ID header, or the one it has is not valid.Permanent
  36. 550 5.7.1More than one sender in From.Gmail rejected the message because its From header lists more than one address, or the message has more than one From header.Permanent
  37. 550 5.7.1Unicode character in a header.Gmail rejected the message because a header that must stay plain ASCII contains a Unicode character.Permanent
  38. 550 5.7.1Duplicate headers.Gmail rejected the message because a header that may appear only once, such as Subject or Date, appears more than once.Permanent
  39. 550 5.7.1Invalid domain in the From header.Gmail rejected the message because the domain in its From address is not written in a form that RFC 5322 allows.Permanent
  40. 550 5.7.1Rejected under a rate limit.Gmail rejected this message under a rate limit, and links the reply to its page on limits for sending and getting email.Permanent
  41. 550 5.7.1IP not authorized to send directly.Gmail will not accept mail sent straight from your IP, typically a home or dynamic address, and asks you to send through your provider's mail server.Permanent
  42. 550 5.7.1Daily relay limit reached for the customer.Your Google Workspace organization has relayed as much mail through smtp-relay.gmail.com today as its daily limit allows.Permanent
  43. 550 5.7.1Encoded word in a header where it is not allowed.Gmail rejected the message because a header contains RFC 2047 encoded-word text in a place where that encoding is not allowed.Permanent
  44. 550 5.7.1Malformed header.Gmail rejected the message because one of its header lines is malformed under RFC 5322; the bounce names which header it is.Permanent
  45. 550 5.7.24Suspicious SPF record, blocked.Gmail rejected the message because the SPF record of the sending domain contains entries that Gmail considers suspicious.Permanent
  46. 550 5.7.25No PTR record, blocked.Gmail rejected the message because the sending IP has no reverse DNS record, or the hostname in that record does not point back to the IP.Permanent
  47. 550 5.7.26Unauthenticated sender, blocked.Gmail rejected the message because it passed neither SPF nor DKIM, and Gmail requires every sender to pass at least one.Permanent
  48. 550 5.7.26SPF hard fail.Gmail rejected the message because the sending IP is not allowed by the SPF record of the envelope domain, and that record ends in -all.Permanent
  49. 550 5.7.26Rejected under the sender's DMARC policy.Gmail rejected the message because it failed DMARC, and the From domain's DMARC policy tells receivers to refuse mail that fails.Permanent
  50. 550 5.7.27SPF did not pass, blocked.Gmail rejected the message because it failed SPF, which Gmail requires of bulk senders along with DKIM.Permanent
  51. 550 5.7.28Unsolicited mail from your IP, blocked.Gmail has blocked mail from your IP because of an unusual rate of unsolicited mail from it. It is the permanent counterpart of the 421 4.7.28 limits.Permanent
  52. 550 5.7.29Not sent over TLS, blocked.Gmail rejected the message because your server delivered it without TLS encryption, which Google's sender guidelines require.Permanent
  53. 550 5.7.30DKIM did not pass, blocked.Gmail rejected the message because it failed DKIM, which Gmail requires of bulk senders along with SPF.Permanent
  54. 550 5.7.40No DMARC record, blocked.Gmail rejected the message because the sending domain has no DMARC record, or its record has no policy, which Gmail requires of bulk senders.Permanent
  55. 552 5.2.2Mailbox full and inactive.The recipient's Google account is out of storage and no longer in use, so Gmail rejected your message permanently.Permanent
  56. 552 5.3.4Message too large.The message, with its attachments, is larger than Gmail accepts, so it was rejected and needs to be made smaller or sent another way.Permanent
  57. 552 5.3.4Too many attachments.Gmail rejected the message because it carries more attachments than Google allows in one message, whatever their size.Permanent
  58. 552 5.3.4Message headers too large.Gmail rejected the message because its header section as a whole is larger than Google allows, or holds too many header fields.Permanent
  59. 552 5.3.4A single header is too large.Gmail rejected the message because one of its header fields holds a value longer than Google allows for a single header.Permanent
  60. 552 5.3.4Header name too long.Gmail rejected the message because the name of one of its header fields is longer than Google allows.Permanent
  61. 552 5.3.4Subject line too long.Gmail rejected the message because its Subject header is longer than Google's header size limits allow.Permanent
  62. 552 5.7.0Blocked for a potential security issue.Gmail blocked the message because something in it, typically an attachment, looks like a security risk under its content and attachment rules.Permanent
  63. 553 5.1.2Recipient domain not found.Gmail could not find the domain in the recipient address, so it has nowhere to deliver the message and rejected it.Permanent
  64. 553 5.1.3Recipient address is not valid.Gmail rejected the recipient address because it is not written in a form the SMTP standard allows, so nothing can be sent to it.Permanent
  65. 553 5.1.7Sender address is not valid.Gmail rejected the address in your MAIL FROM command because it does not follow the SMTP address syntax, so it will not take mail from it.Permanent
  66. 554 5.4.6Mail loop detected.The message passed through more than 50 mail servers on its way, which usually means it is stuck in a loop, so Gmail stopped it.Permanent
  67. 554 5.6.0Malformed message.Gmail refused the message because its structure breaks the Internet Message Format rules of RFC 5322, so it cannot be read reliably.Permanent
  68. 554 5.7.0Too many unauthenticated commands.Gmail closed the session because your client sent too many commands without signing in, on a service that needs authentication.Permanent
  69. 555 5.5.2Syntax error in a command.Gmail could not parse a command or its parameters from your client, usually MAIL FROM or RCPT TO, and refused it.Permanent

Temporary failures (4xx)

39 codes

The receiving server cannot take the message now. Your server keeps it and retries, and only bounces it if the retries run out.

  1. 4.7.31No DMARC record, in Google's FAQ.Google's sender guidelines FAQ lists 4.7.31 for mail rate limited because the sending domain has no DMARC record, or has one without a policy.Temporary
  2. 421 4.3.0Temporary system problem.Gmail closed the connection because of a passing problem on its own systems. The reply points at Google's side, and a retry should deliver the message.Temporary
  3. 421 4.4.5Server busy.The Gmail server you reached was too busy to take your connection and asked you to come back later. Your server should retry on its own.Temporary
  4. 421 4.7.0Connection expired.Gmail closed an SMTP connection that had been open too long, and asks your server to open a new one and send again.Temporary
  5. 421 4.7.0Sending IP not on the domain's allowlist.The Google Workspace domain you are writing to only accepts mail from listed IP addresses, and the IP you send from is not one of them.Temporary
  6. 421 4.7.0Try again later, closing connection.Gmail ended your session at one SMTP command and asked you to come back later, without giving a reason. It is a temporary deferral.Temporary
  7. 421 4.7.0No PTR record for the sending IP.Gmail is rate limiting mail from your IP because it has no reverse DNS name, or that name does not point back to the same IP.Temporary
  8. 421 4.7.0TLS required by the recipient's domain.The Workspace domain you are writing to only accepts mail over an encrypted connection, and your server tried to deliver without TLS.Temporary
  9. 421 4.7.0Low IP reputation, rate limited.Gmail is rate limiting mail from your sending IP because that IP has a very low reputation with Gmail.Temporary
  10. 421 4.7.0Low domain reputation.Gmail has turned away this message because the domain it comes from has a very low reputation with Gmail.Temporary
  11. 421 4.7.0Suspicious content or links.Gmail blocked this message because something in its text or its links looks like spam or abuse to Gmail's filters.Temporary
  12. 421 4.7.26Unauthenticated mail, rate limited.Gmail is slowing mail from you because this message passed neither SPF nor DKIM, and Gmail requires every sender to pass at least one.Temporary
  13. 421 4.7.27SPF did not pass, rate limited.Gmail is rate limiting your mail because it failed SPF, which Gmail requires of bulk senders, those sending more than 5,000 messages a day to Gmail.Temporary
  14. 421 4.7.28Unusual rate of mail.Gmail saw an unusual rate of mail from you and has temporarily rate limited it, to protect its users from possible spam.Temporary
  15. 421 4.7.28Unusual rate of mail from your IP.Gmail is rate limiting mail from one of your sending IP addresses because the rate of mail it sees from that IP is unusual.Temporary
  16. 421 4.7.28Unsolicited mail from your IP netblock.Gmail is rate limiting a whole range of IP addresses that includes yours, because of the rate of unsolicited mail coming from that range.Temporary
  17. 421 4.7.28Unsolicited mail from your DKIM domain.Gmail is rate limiting mail signed with your DKIM domain, because it sees an unusual rate of unsolicited mail carrying that signature.Temporary
  18. 421 4.7.28Unsolicited mail from your SPF domain.Gmail is rate limiting mail whose envelope domain passes SPF, because it sees an unusual rate of unsolicited mail from that domain.Temporary
  19. 421 4.7.28Unsolicited mail containing your link domain.Gmail is rate limiting messages that link to one of your domains, because that domain appears in an unusual rate of unsolicited mail.Temporary
  20. 421 4.7.28Unsolicited mail from your IP, temporarily blocked.Gmail has temporarily stopped accepting mail from your IP, which goes further than a rate limit, because of the amount of unsolicited mail it has seen from it.Temporary
  21. 421 4.7.28Too many messages with the same Message-ID.Gmail is turning away further copies of a message because you have sent too many messages that carry the same Message-ID header.Temporary
  22. 421 4.7.29Not sent over TLS, rate limited.Gmail is rate limiting your mail because your server delivered it without TLS encryption, which Google's sender guidelines require.Temporary
  23. 421 4.7.30DKIM did not pass, rate limited.Gmail is rate limiting your mail because it failed DKIM, which Google requires of bulk senders along with SPF.Temporary
  24. 421 4.7.32From domain not aligned, rate limited.Gmail is rate limiting your mail because the domain in its From address matches neither the domain that passed SPF nor the one that signed DKIM.Temporary
  25. 421 4.7.40No DMARC record, rate limited.Gmail is rate limiting your mail because the sending domain has no DMARC record, or its record sets no policy, which Gmail requires of bulk senders.Temporary
  26. 450 4.2.1Recipient is receiving mail too fast.Gmail is holding back your message because the recipient's mailbox is taking in mail faster than Google allows, so your server should try again later.Temporary
  27. 450 4.2.1Peak SMTP relay limit exceeded.Your Google Workspace organization is sending through smtp-relay.gmail.com faster than its peak relay limit allows, so Google is deferring relay mail for now.Temporary
  28. 451 4.3.0Message temporarily rejected.Gmail turned your message away for now without giving a reason. It is a temporary failure, and your server should try it again later.Temporary
  29. 451 4.3.0Several recipient domains in one transaction.Your server put recipients at more than one domain into a single SMTP transaction with Gmail, which Gmail does not support, so it asks for a retry.Temporary
  30. 451 4.4.2Connection timed out.Gmail waited too long for your server to send the next command or the message data, and dropped the connection. The message should be retried.Temporary
  31. 451 4.5.0SMTP protocol violation.Your server sent Gmail something that breaks the rules of the SMTP standard, RFC 5321, so Gmail stopped the transaction with a temporary error.Temporary
  32. 451 4.7.23No PTR record, rate limited.Gmail is rate limiting mail from your IP because its reverse DNS record is missing or does not resolve back to the same address.Temporary
  33. 451 4.7.24Suspicious entries in your SPF record.Gmail found something in the sending domain's SPF record that it considers suspicious, and is rate limiting mail from your IP until it is fixed.Temporary
  34. 451 4.7.26DMARC check hit a DNS failure.Gmail could not finish checking SPF and DKIM because a DNS lookup failed, and the From domain's DMARC policy says to reject mail that does not authenticate.Temporary
  35. 452 4.2.2Recipient's mailbox is full.The Gmail or Workspace account you wrote to has run out of storage, so Gmail is deferring your message until the owner frees up space.Temporary
  36. 452 4.5.3Recipient needs its own transaction.The receiving domain's policy settings mean Gmail cannot take this recipient in the same transaction as the others, so it asks you to retry it separately.Temporary
  37. 452 4.5.3Too many recipients.Your message lists more recipients than Gmail accepts at once, so the extra recipients are deferred and need to go in a separate transaction.Temporary
  38. 454 4.7.0Too many sign-in attempts.Gmail is refusing SMTP sign-ins from your client for a while, because it tried to authenticate too many times in a short period.Temporary
  39. 454 4.7.0Sign-in failed on a temporary problem.Gmail could not complete your client's SMTP sign-in because of a passing problem on its side, and asks it to try again later.Temporary

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