Sir,
i have checked documentation of API and your requirement. i can do this work as per your requirement. here is how things will will
1) you need to have a server, where file can be uploaded,
2) file uploaded will be uploaded to Elastic Email and and mail-merge will be called to email
3) i am assuming here that CSV file be in required format , which is {"ToEmail","FirstName","LastName"}
4) you will provide API access for testing and development.
i have 10+ year experience working with PHP applications and i am good with APIs, some of API integrtion i have worked on
USPS,UPS,Fedex,rackspace, salesforce etc.
if you have any questions, please let me know
Thanks and Regards,
Lokesh