vCenter Server Alarm Email Notifications Failing Due to SMTP Connectivity Issues

Products

• VMware vCenter Server

Issue/Introduction

This article describes the steps to troubleshoot and resolve issues where VMware vCenter Server fails to send configured alarm email notifications, such as vCenter Certificate Expiry warnings. This behavior is typically characterized by the absence of expected email alerts despite proper configuration within the vCenter Server Management interface

Environment

VMware vCenter Server

Cause

The primary cause of this issue is typically a network connectivity failure between the vCenter Server appliance and the target SMTP server. If the appliance cannot reach the configured SMTP server and port, the alarm subsystem cannot hand off the notification, resulting in failed delivery.

Resolution

Before proceeding, ensure you have verified your SMTP server settings in the vCenter Server Management interface.

Prerequisites

• Ensure you have the IP address and the specific port number of your target SMTP server.
• Verify that the vCenter Server appliance has the necessary network permissions to communicate with the SMTP server.

Steps to Resolve

1. Test SMTP Connectivity: Log in to the vCenter Server appliance via SSH and run the following command to test connectivity to the SMTP server and port:
   bash
   

   curl -v telnet://<SMTP_Server_IP>:<Port_Number>

• Successful: You should see a response indicating a successful connection (e.g., Connected to <SMTP_Server_IP>).
• Failed: If the connection times out or is refused, the issue is confirmed as a network path failure.

2. Verify Firewall and Network Rules: If the test in Step 1 fails, review your network firewall rules. Ensure that traffic originating from the vCenter Server appliance is permitted to reach the SMTP server on the configured port.
3. Validate Alarm Configuration: Once network connectivity is restored, trigger a test alarm (e.g., by enabling SSH) to verify that the vCenter Server now successfully dispatches the alarm email.