Amazon Simple Email Service
Developer Guide

SMTP Response Codes Returned by Amazon SES

This topic contains a list of response codes that the Amazon SES SMTP interface returns.

You should retry SMTP requests that receive 400 errors. We recommend that you implement a system that retries requests with progressively longer waits (for example, wait 5 seconds before retrying, then wait 10 seconds, and then wait 30 seconds). If the third retry doesn't succeed, wait 20 minutes, and then repeat the process. To see an example of an implementation that uses an exponential retry policy, see How to handle a "Throttling - Maximum sending rate exceeded" error on the AWS Messaging and Targeting Blog.


AWS SDKs implement retry logic automatically, but they use the HTTPS interface instead of SMTP.

If you receive a 500 error, you have to revise your request to correct an issue before you submit the request again. For example, if your AWS authentication credentials are invalid, you have to update your application to use the correct credentials before you submit your request again.

Description Response code More information

Authentication successful

235 Authentication successful

Your SMTP client successfully connected and signed in to the SMTP server.

Successful delivery

250 Ok MessageID

MessageID is a unique string of characters that Amazon SES uses to identify a message.

Service unavailable

421 Too many concurrent SMTP connections

Amazon SES can't process the request because there are currently too many connections to the SMTP server.

Local processing error

451 Temporary service failure

Amazon SES couldn't process the request. There might be issues with the request that prevent it from being processed.


451 Timeout waiting for data from client

Too much time elapsed between requests, so the SMTP server closed the connection.

Daily sending quota exceeded

454 Throttling failure: Daily message quota exceeded

You've exceeded the maximum number of emails that Amazon SES permits you to send in a 24-hour period. For more information, see Managing Your Amazon SES Sending Limits.

Maximum send rate exceeded

454 Throttling failure: Maximum sending rate exceeded

You've exceeded the maximum number of emails that Amazon SES permits you to send per second. For more information, see Managing Your Amazon SES Sending Limits.

Amazon SES issue when validating SMTP credentials

454 Temporary authentication failure

Issues that could cause this issue include (but aren't limited to):

Problem receiving the request

454 Temporary service failure

Amazon SES didn't successfully receive the request. As a result, the message wasn't sent.

Incorrect credentials

530 Authentication required

The application that you use to send email didn't attempt to authenticate when it connected to the Amazon SES SMTP interface. For an example of how to set up an email-sending application to authenticate with Amazon SES, see Configuring Email Clients to Send Through Amazon SES.

Authentication Credentials Invalid

535 Authentication Credentials Invalid

The application that you use to send email didn't provide the correct SMTP credentials to Amazon SES. Note that your SMTP credentials aren't the same as your AWS credentials. For more information, see Obtaining Your Amazon SES SMTP Credentials.

Account not subscribed to Amazon SES

535 Account not subscribed to SES

The AWS account that owns the SMTP credentials is not signed up for Amazon SES.

User not authorized to call the Amazon SES SMTP endpoint

554 Access denied: User UserARN is not authorized to perform ses:SendRawEmail on resource IdentityARN

The AWS Identity and Access Management (IAM) policy or the Amazon SES sending authorization policy of the user who owns the SMTP credentials isn't allowed to call the Amazon SES SMTP endpoint.

Unverified email address

554 Message rejected: Email address is not verified. The following identities failed the check in region region: identity0, identity1, identity2

You're trying to send email from an email address or domain that isn't verified to send email from your Amazon SES account. This error could apply to the "From", "Source", "Sender", or "Return-Path" addresses. If your account is still in the sandbox, you also have to verify every recipient email address (except for the recipients provided by the Amazon SES mailbox simulator). If Amazon SES isn't able to show all of the identities that failed the verification check, the error message ends with three periods (...).


Amazon SES has endpoints in several AWS Regions, and email address verification status is separate for each AWS Region. You have to complete the verification process for each sender in the AWS Regions that you want to use.