For recurring donations, Donorbox has a true/false attribute called Is Recurring Donation. You can map this attribute to a Salesforce field of your choosing. The mapping option is under the standard field mapping page: https://donorbox.org/org_admin/salesforce_settings/new. 
Note that we do now support the legacy Salesforce NPSP Recurring Donations object. It is a feature that can be enabled by Donorbox admin for your org. Please reach out to support@donorbox.org if you would like to sync your Donorbox recurring donations to Salesforce recurring donations object. Further details related to Salesforce recurring donations sync can be found on https://donorbox.org/nonprofit-blog/sync-donorbox-recurring-plans-with-salesforce-recurring-donations/
Details related to data mapping can be found in the following guide: https://donorbox.org/nonprofit-blog/salesforce-data-mapping-guide/
We are also in the process of providing support for the enhanced recurring donations object right now but as of now it is not yet supported.