Hi,
We will use number of email sending server with lot of ips with different server location to do this job. The ips will be rotating so will increase the inbox.
I can provide you a email panel on my server with full of feature like upload a csv email data sheet, emailer design html, you can view how it will look on outlook, gmail, yahoo etc, and you can get the full report regarding the delivery of emails.
If required or you don't have time i can do this work for you.
We can send unlimited that will go to inbox.
Have any query ? please let me know.