In SOI SMTP configuration page, there is no field for "user" configuration - there is only "SMTP email from" field, which does not allow you to enter a user without @domain.com
SOI 4.2 CUX
SMTP configuration
A user and password can be configured directly in the SOI email configuration file located in the below locations:
CA\SOI\tomcat\custom\email-config.xml
CA\SOI\SamUI\custom\email-config.xml
The following rows need to be updated:
<smtp-password>password</smpt-password>
<smtp-mail-from>username</smtp-mail-from>
You can encrypt the password using the command below -
CA\SOI\Tools>EncryptSAMCreds.bat <plain-password>
IMPORTANT: after saving a file, you must restart all SOI services, so a new config can kick in.