Multiple SMTP Per Tenant
Goal: Functional
Developer: Nicolas Micoud
Feature Ticket: IDEMPIERE-4866
Sponsor: T.G.I.
Description:
Since v9, is possible to define several SMTP servers per tenant. Fill usual data (host, port, ...) and then "Used by email or domain" field:

If you fill it with an email address, the server will only be used when an email is sent using this 'from' address. If you fill it with a domain, the server will be used for all email with a 'from' address using this domain.
nb: the program starts to check for the EMail address and if not found, check for the domain.
Source: Wiki