Configuring X-Original-IP header name
When composing email message and sending it out, MailSuite Pro can include a header which holds IP address of user sending the email, as opposed to IP address of MailSuite Pro installation.
In current version of the product, the feature is disabled by default. You can enable it by supplying non-empty XOriginatingIPHeaderName value in data/settings/modules/Mail.config.json
configuration file, typical name for this header is "X-Original-IP". Supplying an empty value means such a header will not be added to outgoing mails.
NB: If the above value is missing in your configuration file, make sure you're on the latest version, and try clicking "Update configuration" button in Database Settings screen of MailSuite Pro admin interface.