Email Notifications from vCenter Server stopped working with error TLS Handshake Failed

Products

• VMware vCenter Server

Issue/Introduction

• Similar logs are observed in vCenter Server Appliance logs /var/log/vmware/messages.log.
  YYYY-MM-DDTHH:MM:SS.975870+00:00 vCenter sendmail[440576]: ruleset=tls_server, arg1=SOFTWARE, relay=[Email Server IP], reject=454 4.7.0 TLS handshake failed.
YYYY-MM-DDTHH:MM:SS.975913+00:00 vCenter sendmail[440576]: 47D5SZBp352671: to=<[email protected]>, delay=00:59:58, xdelay=00:00:00, mailer=relay, pri=122379, relay=[Email Server IP] [Email Server IP], dsn=4.7.0, stat=Deferred: 454 4.7.0 TLS handshake failed.
YYYY-MM-DDTHH:MM:SS.981607+00:00 vCenter sendmail[440576]: 47D5SZBl352671: to=<[email protected]>, delay=01:00:00, xdelay=00:00:00, mailer=relay, pri=122382, relay=[Email Server IP], dsn=4.7.0, stat=Deferred
  
  

Environment

vCenter Server Appliance

Cause

The issue can be caused by one of the following reasons on the mail relay server:
    • The Mail server could be experiencing Time synchronization issues.
    • There is a replication issue between the domain controllers.
    • The Mail server is experiencing Service Principal Name (SPN) issues.
    • The required TCP/UDP ports for the Kerberos protocol are blocked by the firewall.

Resolution

SSL Handshake from the vCenter Server Appliance is being rejected by the Mail relay server. Investigate from the Mail relay server side.

Additional Information

Run the following command from vCenter Server Appliance - SSH to send a test email to the recipient for investigating mail delivery issues.

echo "Subject: sendmail test" | sendmail -v <[email protected]>