19068 Email sending software

we have an email sending script which can be seen here, [login to view URL] we have made a few adjustments to allow us to upload our HTML template to our server and send it via the script, however we can only send about 50 before it times out, we dont want to over use the server so weve tried limiting the number of emails sent per 2 seconds, however this just makes it time out. We need to be able to send 1000 emails at a time without it timing out, or sending duplicates. Ive seen a similar script which allows for such actions at [login to view URL] their script has a Bulk Sending algorithm which divides the total number of subscribers into smaller cycle such as 5, 10, 20, etc. each Process window will automatically refresh itself upon each cycle until the entire process is completed. Anybody who thinks they can solve this please quote here.