Follow the instructions in the Lotus Domino Server documentation page Configuring Domino to send mail to a relay host or firewall.
Where it is asks for Relay host for messages leaving the local Internet domain, enter the value mail.smtp2go.com.
If that doesn’t work, enter the value [188.8.131.52].
When entering an IP address as above, square brackets [ ] are part of the value, so be sure to include them.
Within the configuration document of your server (not the server document) there is a section for Router/SMTP.
Go to the Router/SMTP tab, Restrictions and controls tab, SMTP Inbound controls tab, Inbound Intended Recipients Controls section.
Set “Verify that local domain recipients exist in the Domino Directory:” to Enabled.
Note: If you see an error ‘550 unable to verify sender address’ when trying to send an email after setting up, this means your ‘From’ email address doesn’t have a valid MX record setup yet. All emails must be sent from an email address that has an MX record at its domain name.
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