In addition to the standard SMTP sending via port 25, 587 subscribers can also use the email sending API for processing basic email transactions. The API documentation can be accessed at https://api.outbound.mailhop.org and the regional endpoints for sending:
https://api.outbound.us.mailhop.org/ - Servers located in Oregon USA
https://api.outbound.eu.mailhop.org/ - Servers located in Franfurt Germany
Use your SMTP credentials to access the sending API.