Gmail SMTP errors and codes

You might see the following error messages and codes when using Gmail with Google Workspace . The messages and codes are helpful tools for diagnosing and troubleshooting email problems.

Gmail appends one or both of the following identifiers to all error messages to show you the source of the error: 

  • gsmtp (Google SMTP) is added to all errors. 
  • gcdp (Google Custom Domain Policies) is added to errors resulting from customized rules created by the administrator. 

For example, "550 5.7.1 This message violates example.com email policy. - gcdp <sessionid> - gsmtp" indicates that the error is a result of a custom rule created by the administrator.

For more information, visit About SMTP error messages.

SMTP error messages

Reply Code

Status Code

Reply Text

450

4.2.1

The user you are trying to contact is receiving mail too quickly. Please resend your message at a later time. If the user is able to receive mail at that time, your message will be delivered. For more information, go to Limits for sending & getting mail.

450

4.2.1

The user you are trying to contact is receiving mail at a rate that prevents additional messages from being delivered. Please resend your message at a later time. If the user is able to receive mail at that time, your message will be delivered. For more information, go to Limits for sending & getting mail

450

4.2.1

Peak SMTP relay limit exceeded for this customer. This is a temporary error. For more information on SMTP relay limits, contact your administrator or go to SMTP relay service error messages.

452

4.2.2

The recipient's inbox is out of storage space. Please direct the recipient to Manage files in your Google Drive storage

451

4.3.0

Mail server has temporarily rejected this message. Go to About SMTP error messages for more information.

451

4.3.0

Multiple destination domains per transaction is unsupported. Please try again. For more information, go to About SMTP error messages and review RFC 5321 specifications.

421

4.3.0

Temporary System Problem. Try again later. For more information, go to About SMTP error messages.

451

4.4.2

Timeout - closing connection. For more information, go to About SMTP error messages

421

4.4.5

Server busy, try again later. For more information, go to About SMTP error messages

451

4.5.0

SMTP protocol violation. For more information, go to About SMTP error messages and review RFC 5321 specifications.

452

4.5.3

Domain policy size per transaction exceeded, please try this recipient in a separate transaction. For more information, go to Message bounced due to a policy rule.

452

4.5.3

Your message has too many recipients. For more information regarding Google's sending limits, go to Limits for sending & getting mail

421

4.7.0

Connection expired, try reconnecting. For more information, go to About SMTP error messages.

421

4.7.0

IP not in whitelist for RCPT domain, closing connection. For more information, go to Allowlists, denylists, and approved senders.

421

4.7.0

Try again later, closing connection. (command) For more information, go to About SMTP error messages

421

4.7.0

The IP address sending this message does not have a PTR record, or the corresponding forward DNS entry does not point to the sending IP. To protect our users from spam, mail sent from your IP address has been temporarily rate limited. For more information, go to Email sender guidelines.

454

4.7.0

Too many login attempts, please try again later. For more information, go to Add Gmail to another email client

454

4.7.0

Cannot authenticate due to a temporary system problem. Try again later. For more information, go to About SMTP error messages.

421

4.7.0

TLS required for RCPT domain, closing connection. For more information, go to Email encryption in transit.

421

4.7.0

This message is suspicious due to the very low reputation of the sending IP address. To protect our users from spam, mail sent from your IP address has been temporarily rate limited. For more information, go to Why has Gmail blocked my messages?.

421

4.7.0

This message is suspicious due to the very low reputation of the sending domain. To best protect our users from spam, the message has been blocked. For more information, go to Why has Gmail blocked my messages?.

421

4.7.0

This message is suspicious due to the nature of the content or the links within. To best protect our users from spam, the message has been blocked. For more information, go to Why has Gmail blocked my messages?.

451 4.7.23

ip-address The sending IP address for this message doesn’t have a PTR record, or the PTR record’s forward DNS entry doesn’t match the sending IP address. To protect users from spam, your email has been temporarily rate limited.

To learn more about IP address requirements for sending to Gmail, visit the IP addresses section of our sender guidelines. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.

451

4.7.24

The SPF record of the sending domain has one or more suspicious entries. To protect our users from spam, mail sent from your IP address has been temporarily rate limited. For more information, go to Email sender guidelines.

451

4.7.26

Unauthenticated email from domain-name is not accepted due to domain's DMARC policy, but temporary DNS failures prevent authentication. Please contact the administrator of domain-name domain if this was a legitimate mail. To learn about the DMARC initiative, go to Gmail Help.

421

4.7.26

This mail has been rate limited because it is unauthenticated. Gmail requires all senders to authenticate with either SPF or DKIM. Authentication results: DKIM = did not pass SPF domain-name with ip: ip-address = did not pass. To resolve this issue, go to Email sender guidelines

421

4.7.27

Your email has been rate limited because SPF authentication didn't pass for this message. Gmail requires all bulk email senders to authenticate their email with SPF. Authentication results: SPF domain-name with IP address: ip-address = Did not pass.

To set up SPF for your sending domains, visit Define your SPF record. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.

421

4.7.28

Gmail has detected an unusual rate of mail. To protect our users from spam, mail has been temporarily rate limited. To review our bulk email senders guidelines, go to Email sender guidelines.

421

4.7.28

Gmail has detected an unusual rate of mail originating from your IP address ip-address. To protect our users from spam, mail sent from your IP address has been temporarily rate limited. To review our bulk email senders guidelines, go to Email sender guidelines.

421

4.7.28

Gmail has detected an unusual rate of unsolicited mail originating from your IP Netblock ip-address. To protect our users from spam, mail sent from your IP Netblock has been temporarily rate limited. To review our bulk email senders guidelines, go to Email sender guidelines.

421

4.7.28

Gmail has detected an unusual rate of unsolicited mail originating from your DKIM domain domain-name. To protect our users from spam, mail sent from your domain has been temporarily rate limited. To review our bulk email senders guidelines, go to Email sender guidelines.

421

4.7.28

Gmail has detected an unusual rate of unsolicited mail originating from your SPF domain domain-name. To protect our users from spam, mail sent from your domain has been temporarily rate limited. To review our bulk email senders guidelines, go to Email sender guidelines.

421

4.7.28

Gmail has detected an unusual rate of unsolicited mail containing one of your URL domains. To protect our users from spam, mail with the URL has been temporarily rate limited. To review our bulk email senders guidelines, go to Email sender guidelines.

421

4.7.28

Gmail has detected an unusual amount of unsolicited mail originating from your IP address. To protect our users from spam, mail sent from your IP address has been temporarily blocked. To review our bulk email senders guidelines, go to Email sender guidelines.

421

4.7.28

Gmail has detected this message exceeded its quota for sending messages with the same Message-ID:. To best protect our users, the message has been temporarily rejected. For more information, go to Why has Gmail blocked my messages?.

421

4.7.29

Your email has been rate limited because this message wasn’t sent over a TLS connection. Gmail requires all bulk email senders to use TLS/SSL for SMTP connections.

To set up TLS for email, visit TLS & SSL connections. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.

421 4.7.30

Your email has been rate limited because DKIM authentication didn't pass for this message. Gmail requires all email bulk senders to authenticate their email with DKIM. Authentication results: DKIM = Did not pass.

To set up DKIM for your sending domains, visit Turn on DKIM for your domain. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.

421 4.7.32

Your email has been rate limited because the From: header (RFC5322) in this message isn’t aligned with either the authenticated SPF or DKIM organizational domain.

To learn more about DMARC alignment, visit Define your DMARC record. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.

550

5.1.1

The email account that you tried to reach does not exist. Please double-check the recipient's email address for typos or unnecessary spaces. For more information, go to Fix bounced or rejected emails

553

5.1.2

We weren't able to find the recipient domain. Please check for any spelling errors and make sure you didn't enter any spaces, periods, or other punctuation after the recipient's email address. For more information, go to Fix bounced or rejected emails

553

5.1.3

The recipient address address is not a valid RFC 5321 address. For more information, go to About SMTP error messages and review RFC 5321 specifications.

553

5.1.7

The sender address address is not a valid RFC 5321 address. For more information, go to About SMTP error messages and review RFC 5321 specifications.

550

5.2.1

The email account that you tried to reach is inactive. For more information, go to https://support.google.com/mail/?p=DisabledUser

550

5.2.1

The user you are trying to contact is receiving mail at a rate that prevents additional messages from being delivered. For more information, go to Limits for sending & getting mail

552

5.2.2

The recipient's inbox is out of storage space  and inactive. Please direct the recipient to Manage files in your Google Drive storage

552

5.3.4

Your message exceeded Google's message size limits. To view our message size guidelines, go to Send attachments with your Gmail message.

552

5.3.4

The number of attachments (num-attachments) exceeds Google's limit of limit attachments. To view our attachment size guidelines, go to Gmail receiving limits in Google Workspace.

552

5.3.4

The size of your message (size bytes) exceeded Google's message size limits of limit bytes. To view our message size guidelines, go to Gmail receiving limits in Google Workspace.

552

5.3.4

Your message exceeded Google's message header size limits. To view our header size guidelines, go to Gmail message header limits.

552

5.3.4

Your message exceeded Google's message header size limits. Messages must not exceed limit total header bytes or limit header fields. To view our header size guidelines, go to Gmail message header limits.

552

5.3.4

The size of the header name header value (size bytes) exceeds Google's limit of limit bytes per individual header size. To view our header size guidelines, go to Gmail message header limits.

552

5.3.4

The size of one of the header values (size bytes) exceeds Google's limit of limit bytes per individual header size. To view our header size guidelines, go to Gmail message header limits.

552

5.3.4

The size of a header name (size bytes) exceeds Google’s header name limit of limit bytes. To view our header size guidelines, go to Gmail message header limits.

552

5.3.4

Your message has a Subject: header that exceeds Google's message header size limits. To view our header size guidelines, go to Gmail message header limits.

550

5.4.5

Daily user sending limit exceeded. For more information on Gmail sending limits, go to Gmail sending limits.

550

5.4.5

Daily SMTP relay limit exceeded for user. For more information on SMTP relay sending limits, contact your administrator or go to SMTP relay service error messages

554

5.4.6

Message exceeded 50 hops, this may indicate a mail loop. For more information, go to Gmail Help

503

5.5.1

Bad sequence of commands. For more information, go to About SMTP error messages and review RFC 5321 specifications.

502

5.5.1

Unimplemented command. For more information, go to About SMTP error messages.

502

5.5.1

Unrecognized command. For more information, go to About SMTP error messages.

502

5.5.1

Too many unrecognized commands, goodbye. For more information, go to About SMTP error messages.

503

5.5.1

No DATA after BDAT. A mail transaction protocol command was issued out of sequence. For more information, go to About SMTP error messages and review RFC 3030 specifications.

503

5.5.1

EHLO/HELO first. A mail transaction protocol command was issued out of sequence. For more information, go to HELO/EHLO email error.

503

5.5.1

MAIL first. A mail transaction protocol command was issued out of sequence. For more information, go to About SMTP error messages and review RFC 5321 specifications.

503

5.5.1

RCPT first. A mail transaction protocol command was issued out of sequence. For more information, go to About SMTP error messages and review RFC 5321 specifications.

501

5.5.2

Syntax error, cannot decode response. For more information, go to About SMTP error messages.

555

5.5.2

Syntax error. For more information, go to About SMTP error messages and review RFC 5321 specifications.

555

5.5.2

Syntax error, goodbye. For more information, go to About SMTP error messages and review RFC 5321 specifications.

550

5.5.3

Too many recipients for this sender. For more information, go to About SMTP error messages and review RFC 5321 specifications.

501

5.5.4

HELO/EHLO argument argument invalid closing connection. For more information, go to HELO/EHLO email error.

501

5.5.4

Empty HELO/EHLO argument not allowed, closing connection. For more information, go to HELO/EHLO email error.

554

5.6.0

Mail message is malformed. Not accepted. For more information, go to Email sender guidelines and review RFC 5322 specifications.

552

5.7.0

This message was blocked because its content presents a potential security issue. To review our message content and attachment content guidelines, go to File types blocked in Gmail.

503

5.7.0

No identity changes permitted. For more information, go to About SMTP error messages.

550

5.7.0

Mail relay denied ip-address. Invalid credentials for relay for one of the domains in: domain-name (as obtained from HELO and MAIL FROM). Email is being sent from a domain or IP address which isn't registered in your Workspace account. Please login to your Workspace account and verify that your sending device IP address has been registered within the Workspace SMTP Relay Settings. For more information, go to SMTP relay service error messages

550

5.7.0

Mail relay denied ip-address. The sending mail account has been temporarily suspended due to abuse. For more information, go to SMTP relay spam policy in Gmail.

550

5.7.0

Mail sending denied. For more information, go to SMTP relay service error messages

554

5.7.0

Too many unauthenticated commands. For more information, go to About SMTP error messages.

530

5.7.0

Authentication required. For more information, go to Can't sign in to your Google Account

530

5.7.0

Must issue a STARTTLS command first. For more information, go to About SMTP error messages and review RFC 3207 specifications.

552

5.7.0

This message was blocked because its content presents a potential security issue. To review our message and attachment content guidelines, go to File types blocked in Gmail.

550

5.7.1

The user or domain that you are sending to (or from) has a policy that prohibits the mail that you sent. Contact your domain administrator for assistance. For more information, go to Sorry, a policy is in place that prevents your message from being sent

550

5.7.1

Invalid credentials for relay ip-address. The IP address you've registered in your Workspace SMTP Relay service doesn't match the domain of the account this email is being sent from. If you are trying to relay mail from a domain that isn't registered under your Workspace account or has empty envelope-from:, you must configure your mail server either to use SMTP AUTH to identify the sending domain or to present one of your domain names in the HELO or EHLO command. For more information, go to SMTP relay service error messages

550

5.7.1

This message is likely unsolicited mail. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Why has Gmail blocked my messages?.

550

5.7.1

This message does not meet IPv6 sending guidelines regarding PTR records and authentication. For more information, go to Email sender guidelines.

550

5.7.1

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. For more information, go to Why has Gmail blocked my messages?.

550

5.7.1

This message is likely suspicious due to the very low reputation of the sending domain. To best protect our users from spam, the message has been blocked. For more information, go to Why has Gmail blocked my messages?.

550

5.7.1

Messages missing a valid address in the From: header, or having no From: header, are not accepted. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

Messages missing a valid Message-ID: header are not accepted. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

Messages with multiple addresses in the From: header are not accepted. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

The message contains a unicode character in a disallowed header. To review our message and header content guidelines, go to File types blocked in Gmail.

550

5.7.1

This message is not RFC 5322 compliant because it has duplicate headers. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

This message is not RFC 5322 compliant because the From: header is missing. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

This message is not RFC 5322 compliant because it has multiple From: headers. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

This message is not RFC 5322 compliant because the From: header has a non-compliant domain name. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

This mail has been rate limited  . For more information, go to Limits for sending & getting mail

550

5.7.1

The IP you're using to send mail is not authorized to send email directly to our servers. Use the SMTP relay at your service provider instead. For more information, go to 'The IP you're using to send email is not authorized...'

550

5.7.1

Daily SMTP relay sending limit exceeded for this customer. For more information on SMTP relay sending limits, contact your administrator or visit SMTP relay service error messages

550

5.7.1

Encoded-word syntax is not permitted in message header header-name. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

This message is not RFC 5322 compliant. There are multiple header-name headers. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.

550

5.7.1

This message is not RFC 5322 compliant. There is a malformed header- name header. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.

523

5.7.10

SMTP protocol violation, no commands allowed to pipeline after STARTTLS. For more information, go to About SMTP error messages and review RFC 3207 specifications.

501

5.7.11

Syntax error (no parameters allowed). For more information, go to About SMTP error messages and review RFC 3207 specifications.

534

5.7.14

Please log in through your web browser and then try again. For more information, go to Can't sign in to your Google Account

550

5.7.24

The SPF record of the sending domain has one or more suspicious entries. For more information, go to Email sender guidelines.

550

5.7.25

The IP address sending this message does not have a PTR record setup, or the corresponding forward DNS entry does not point to the sending IP. As a policy, Gmail does not accept messages from IPs with missing PTR records. For more information, go to Email sender guidelines.

550

5.7.25

The sending IP does not match the IP address of the hostname specified in the pointer (PTR) record. For more information, go to Email sender guidelines.

550

5.7.26

This mail has been blocked because the sender is unauthenticated. Gmail requires all senders to authenticate with either SPF or DKIM. Authentication results: DKIM = did not pass SPF [domain-name] with ip: [ip-address] = did not pass. For instructions on setting up authentication, go to Email sender guidelines

550

5.7.26

The MAIL FROM domain [domain-name] has an SPF record with a hard fail policy (-all) but it fails to pass SPF checks with the ip: [ip-address]. To best protect our users from spam and phishing, the message has been blocked. For more information, go to Email sender guidelines.

550

5.7.26

Unauthenticated email from domain-name is not accepted due to domain's DMARC policy. Contact the administrator of domain-name domain if this was legitimate mail. To learn about the DMARC initiative, go to Control unauthenticated mail from your domain.

550

5.7.27

This mail has been blocked because SPF does not pass. Gmail requires all large senders to authenticate with SPF. Authentication results: SPF domain-name with ip: ip-address = did not pass. For instructions on setting up SPF authentication, go to Define your SPF record—Basic setup

550

5.7.28

There is an unusual rate of unsolicited mail originating from your IP address. To protect our users from spam, mail sent from your IP address has been blocked. To review our bulk email senders guidelines, go to Email sender guidelines.

550 5.7.29

Your email has been blocked because this message wasn’t sent over a TLS connection. Gmail requires all bulk email senders to use TLS/SSL for SMTP connections.

To set up TLS for email, visit TLS & SSL connections. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.
550 5.7.30 This mail has been blocked because DKIM does not pass. Gmail requires all large senders to authenticate with DKIM. Authentication results: DKIM = did not pass. For instructions on setting up DKIM authentication, go to Turn on DKIM for your domain.   

504

5.7.4

Unrecognized authentication type. For more information, go to About SMTP error messages.

504

5.7.4

XOAUTH is no longer supported. For more information, go to XOAUTH Migration | Gmail | Google for Developers

535

5.7.8

Username and Password not accepted. For more information, go to Can't sign in to your Google Account

534

5.7.9

Application-specific password required. For more information, go to Sign in with app passwords

534

5.7.9

Please log in with your web browser and then try again. For more information, go to Can't sign in to your Google Account

Was this helpful?

How can we improve it?
true
Search
Clear search
Close search
Google apps
Main menu