What to use it for
Host two or more companies in one Exchange server and send out the emails for the two domains through their different web providers.
Support company domain addresses (sending out emails through your regular web space relay) plus a few Google mail addresses (sending out emails through the Gmail servers) on the same machine.
Support sending out from specific different IP addresses – based on the FROM address.

Features:
New (v2.98): Automatic TLS 1.2 and 1.3 support.
Sender-based routing to separate SMTP accounts and servers.
Separate SMTP relay server login data based on sender.
Select local IP address to be used for outgoing email – based on sender
Works with all Exchange versions, include SBS
Supports SSL encrypted connections to SMTP relay servers
No limit to number of different relay servers.
One-off price, no recurring costs.

Home Page - https://www.servolutions.com/multisendcon.htm