To use our Outbound Service as a SmartHost for your Exchange server, do the following:
https://technet.microsoft.com/en-us/library/jj150562(v=exchg.160).aspx
You can use a single login, which will allow all the domains on your account to authenticate, even if the domains aren't the same. As long as they are in the same account. You can also use a quarantine login or any account contact login to authenticate with if you enable the Enable outbound sending for quarantine users and account contacts option on the Outbound settings page.
Switching the outbound connector to use port 587 or 465
Get-SendConnector
Set-SendConnector -identity "SpamHero SmartHost" -Port:587
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