This APSIS One API feature is in development and it's not meant to be used yet
Send a Transactional Email
Sends an existing Transactional Email activity to a single email address provided via the to_email request parameter. This action is also called a transaction.
Sending a transaction generates transactional events related to email sending like "sent", "delivered", "open", etc. These events are created on a profile designated with keyspace_discriminator and profile_key request parameters. If a profile does not exist it is implicitly created.
To work with existing profiles and/or to have access to transactional events, use keyspaces like com.apsis1.keyspaces.email or com.apsis1.keyspaces.crm-id.
If you're not interested in these events, it's best to use com.apsis1.keyspaces.transactional keyspace.
It is not recommended, but if for some reason you are planning to merge profiles from com.apsis1.keyspaces.transactional keyspace with other profiles then be aware of the limitation of 500 profiles that can be merged together. For this reason we DO NOT recommend to create multiple transactional profiles in com.apsis1.keyspaces.transactional keyspace and then merge them with other profiles. Instead, use that other keyspace when sending transactional emails.
The total size of all attachments must not exceed 2 MB.