Hi Please could you confirm the product (HEAT Classic, ITSM or ISM) and version you are using as the answer will vary depending on the platform
Ivanti Service Manager
I will move this post to the correct community area.
The answer to your question is you would run an single STMP mail box for out going mail with a relay or send on behalf of set on the mailbox. You then use business rules/expressions to select the correct out going mail address to use.