Alarms generated on the vCenter server are not reaching the SMTP mail server.

Products

• VMware vCenter Server
• VMware vCenter Server 8.0
• VMware vCenter Server 7.0

Issue/Introduction

vCenter server is configured correctly with the correct mail sender email and when Alarms are generated the summary shows the Alarm is send successfully on the configured email address. 

Environment

vCenter server 7.x.x

vCenter server 8.x.x

Cause

The mails are being blocked on the network.

Resolution

1. We start to check with the journalctl -xe and messages logs on the vCenter server. 
2. Please refer the below log snippets from the working and non-working.

 

Non-working 

/var/log/vmware/messages:

YYYY-MM-DDTHH.MM.SS.491908+05:30 abc-vc01 sendmail[57029]7: to=<[email protected]>, delay=00:00:04, xdelay=00:00:04, mailer=relay, pri=31260, relay=example.mail...ction.outlook.com. [XX.XX.XX.XX], dsn=5.7.1, reply=550 5.7.1 Service unavailable, Client host [XX.XX.XX.XX] blocked using EXAMPLE.
YYYY-MM-DDTHH.MM.SS.335Z 08DD32D509B902D6], stat=User unknown
YYYY-MM-DDTHH.MM.SS.229627+05:30 abc-vc01 sendmail[57029] ############: DSN: User unknownX
YYYY-MM-DDTHH.MM.SS.992184+05:30 abc-vc01 sendmail[57029]:###########: to=<[email protected]>, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=32284, relay=example.mail...ction.outlook.com. [XX.XX.XX.XX.], dsn=5.7.1, reply=550 5.7.1 Service unavailable, Client host [XX.XX.XX.XX] blocked using domain 
YYYY-MM-DDTHH.MM.SS, stat=User unknown
YYYY-MM-DDTHH.MM.SS.7217+05:30 abc-vc01 sendmail[57029:: return to sender: User unknown
YYYY-MM-DDTHH.MM.SS.576946+05:30 abc-vc01 sendmail[57029]: to=root, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=33308, dsn=2.0.0, stat=Sent

Working

/var/log/vmware/messages:

YYYY-MM-DDThh:mm:ss.370170+00:00 <vCenter-01> sendmail[61740]:#########: to=root, ctladdr=root (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=138429, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (Message accepted for delivery)