SMTP relay service error messages

Mail relay denied

• Email is being sent from a domain or IP that isn’t registered in Google Workspace. Please sign in to your Google Workspace account and verify that your sending device IP is registered within Google Workspace SMTP relay service settings. See SMTP Relay service setting for more information.
• The domain with the configured policy couldn't be properly identified. Please ensure that the sending client uses an appropriate value for both the HELO command; ideally, the fully qualified domain name (FQDN) of the sending device, and that the SMTP sender (MAIL FROM:) identifies the send address properly (MAIL FROM: <[e-mail]>). 

Invalid credentials for relay

The IP address you registered in the Google Workspace SMTP relay service setting 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 in your Google Workspace account, 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. See SMTP Relay service setting for more information.

Daily SMTP relay limit exceeded for customer

The customer has reached their daily SMTP relay limit. See SMTP Relay service setting for SMTP relay sending limits, or contact your administrator for additional help.

Peak SMTP relay limit exceeded for customer

This is a temporary error. The customer has exceeded their peak SMTP relay limit, and relay mail for the customer is temporarily being deferred. See SMTP Relay service setting for SMTP relay sending limits.

Daily SMTP relay limit exceeded for user

The user has reached their daily SMTP relay limit. See SMTP Relay service setting for SMTP relay sending limits, or contact your administrator for additional help.

Your message has too many recipients

There is a 100-recipient limit per SMTP transaction for smtp-relay.gmail.com. To send messages to additional recipients, start another transaction (new SMTP connection or RSET command).

Notes:

• Error messages might not always appear. This can happen for a number of reasons. For example, the servers on the sender side might not accept non-deliverable responses (NDRs), or the sending client can’t receive email notification because the sender is a device, such as a printer or scanner.
• If the error messages have reached Google servers, they can be traced in email log search.
• If the sender keeps send logs, they can trace the error messages from their logs.