vCenter Server Appliance email notifications are not sent when multiple email addresses are defined in an alarm action

Products

• VMware vCenter Server

Issue/Introduction

• Alarm Actions are set to send an email notification to multiple email addresses using the semicolon (;) delimiter.
• You see this alarm error:
  
  Alarm 'nameofalarm' on <vCenterServerFQDN> cannot send email to <emailaddress1>;<emailaddress2>;
   
• In the /var/mail/root logs, you see entries similar to:
  

  Final-Recipient: RFC822; <contact1>@<domainname>;<contact2@<domainname>;
X-Actual-Recipient: rfc822; “553 Invalid route address”@<vcsaname>.<domainname>
Action: failed
Status: 5.1.3

Environment

VMware vCenter Server 7.x

VMware vCenter Server 8.x

Cause

VMware vCenter Server Appliance only accepts comma (,) to separate email addresses.

Cause Validation 

Validate VCenter /var/log/messages.log and check for invalid route address and emails are separated with ;

2025-08-21T10:12:11.200528+05:30 TS##-####sendmail[2132023]: 57L4gBP62132023: 57L4gBP72132023: DSN: example.com;example1.com;exapmple2com;... Invalid route address
2025-08-21T10:12:11.302558+05:30 TS####-###sendmail[2132028]: 57L4gBXA2132028: 57L4gBXB2132028: DSN:example.com;example1.com;exapmple2com;... Invalid route address
2025-08-21T10:12:11.364353+05:30 TS##-##-V##1 sendmail[2132041]: 57L4gBud2132041: 57L4gBue2132041: DSN: example.com;example1.com;exapmple2com;;... Invalid route address
2025-08-21T10:12:11.713639+05:30 T####-##sendmail[2132079]: 57L4gBOa2132079: 57L4gBOb2132079: DSN: example.com;example1.com;exapmple2com;... Invalid route address
2025-08-21T10:17:09.628262+05:30 TS##-##-## sendmail[2135827]: 57L4l9Ra2135827: 57L4l9Rb2135827: DSN: example.com;example1.com;exapmple2com;... Invalid route address
2025-08-21T10:17:09.762091+05:30 T##-##-## sendmail[2135832]: 57L4l9Xv2135832: 57L4l9Xw2135832: DSN: example.com;example1.com;exapmple2com;... Invalid route address

Resolution

Email addresses need to be separated by a comma (,). For more information, see: Unable to send a notification email from Alarm action if multiple emails are separated by semicolon

Use comma (,) and not semicolon (;) to separate multiple email addresses in your alarm action.

To workaround,

1. Create multiple email notification actions for each email address.
2. Utilize an email distribution group to send email notifications.