Email blocked with error "460 too many messages (#4.3.0)"

Products

• Email Security.cloud

Issue/Introduction

This error can occur when sending outbound or inbound emails through Email Security.Cloud. A non-delivery receipt (NDR) stating delivery contains a message that the intended recipient has failed with error:

460 too many messages (#4.3.0)

Cause

The sending email server is attempting to send more than 20 individual emails in a single SMTP connection.

This does not include a single email with multiple recipients. An individual email consists of a full set of SMTP commands that specifies the sender, recipients, data, body of the mail, and a single dot sent in a line by itself that signifies to the receiving mail server that the message is completed. If the sending mail server does not close the SMTP connection, it has the option to send a new email. If it does, this will add to the total number of individual emails the server is allowed to send during the SMTP connection, up to 20.

Resolution

The sending mail server must be configured to send 20 or fewer emails per SMTP connection.