e-mail Alert not triggering in vCenter Server Appliance.

Products

• VMware vCenter Server

Issue/Introduction

• The issue occurs when the alarm is triggered in vCenter Server, but Sendmail is not sending the email notifications to the configured recipients. Despite the alarm being triggered, no email is being sent to the specified recipient.
• Below is the example alarm definition set in vCenter, however alert e-mail was not triggered.

In The messages log, you see entries similar to:

YYYY-MM-DD(Time)+08:00 vcs008 sendmail[3631279]: 52L7r0Ai3631276: to=<email.com>, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=121000, relay=webmail.xxx.xxx.xx., dsn=4.4.3, stat=Deferred: Name server: email.com: host name lookup failure
YYYY-MM-DD(Time)+08:00 vcs008 sendmail[3631281]: 52L7r01O3631277: to=<email.com>, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=121100, relay=webmail.xx.xxx.xx., dsn=4.4.3, stat=Deferred: Name server: email.com: host name lookup failure

In The vpxd.log, you see entries similar to:

MM DD Time email.com vpxd[6229]: Event [209710] [1-1] [2025-03-19T07:02:08.925625Z] [vim.event.AlarmActionTriggeredEvent] [info] [] [Cluster_Name] [209710] [Alarm 'VM reboot' on TESTVM-RAID5 triggered an action]
MM DD Time email.com vpxd[6229]: Event [209718] [1-1] [2025-03-19T07:02:09.390829Z] [vim.event.AlarmEmailCompletedEvent] [info] [] [Cluster_Name] [209718] [Alarm 'VM reboot' on TESTVM-RAID5 sent email to email.com]
MM DD Time email.com vpxd[6229]: Event [224691] [1-1] [2025-03-21T07:25:59.326191Z] [vim.event.EventEx] [info] [] [Cluster_Name] [224691] [Alarm 'VM reboot' on WIN_TEST triggered by event 224690 'WIN_TEST on  email.com in Cluster_Name is powered off']
MM DD Time email.com vpxd[6229]: Event [224692] [1-1] [2025-03-21T07:25:59.32636Z] [vim.event.AlarmActionTriggeredEvent] [info] [] [Cluster_Name] [224692] [Alarm 'VM reboot' on WIN_TEST(Test_VM_Name) triggered an action]
MM DD Time email.com vpxd[6229]: Event [224699] [1-1] [2025-03-21T07:25:59.789132Z] [vim.event.AlarmEmailCompletedEvent] [info] [] [Cluster_Name] [224699] [Alarm 'VM reboot' on WIN_TEST(Test_VM_Name) sent email to emai.com]
MM DD Time vCenter_fqdn vpxd[6229]: Event [224741] [1-1] [2025-03-21T07:32:59.468349Z] [vim.event.EventEx] [info] [] [Cluster_Name] [224741] [Alarm 'VM rebo WIN_TEST(Test_VM_Not) triggered by event 224740 

Environment

VMware vCenter Server Appliance 7.0.x

VMware vCenter Server Appliance 8.0.x

Cause

The issue stems from a failure in resolving the name of the mail relay server (email.com). This DNS lookup failure is preventing Sendmail from properly connecting to the server, causing email delivery to be deferred. As a result, email notifications are not being sent.

Resolution

Make sure the domain `email.com` (Mail relay server ) is resolvable.

1.Update the vCenter with nameserver that can resolve domain of the mail server 
2. or add entry to /etc/hosts of the mail server domain (email.com) in the vCenter 

Note: With option 2, whenever the vCenter is upgraded update the host file with the entries again