Notifications app fails with "Error panic: 421 closing connection"

Products

• VMware Tanzu Application Service for VMs

Issue/Introduction

The notifications app log shows the SMTP server error 421 as below:

ERR panic: 421 email-server.addr.com closing connection [recovered]

The most common causes of this error include

1. Too many connections from your host.
2. The server is busy and cannot accept the connection.
3. Service is temporarily unavailable.

Environment

Product Version: 2.13

Resolution

To fix this issue:
1. Review the email user setup and use separate user for each environment.
2. Check the limits set on the email server with regard to the amount of emails it can handle and adjust to allow the workload to run as expected.