I want to send 1000 emails to different people, but not able to know, how to land it in the inbox and not get caught by filters.
If it's a valid list, Mailchip, Aweber, any of those.
For a send that small, though, there are also scripts for Google docs that will send them. I think 1000 would be okay there (I've only used it for about 150 though).
Whether or not it will get caught in a filter will depend on the content of the letter and whether or not these people have previously received mail from you
1,000 is so small that I suggest the same as Ergophobe said, simply use your normal email account.
However if you wanted to go another route than any of the standard SMTP services will do it for you at next to no cost too.