Gmail Reputation problems

I am very dissatisfied about my email reputation, while I sending to gmail mailbox all mails are going to spam folder.

1. First I send 100 mails send out my domain reputation that time was High in gmail postmaster tools,

2. Gradually I increased the volume of mail , 100, 200, 500,1000,2500,...etc,, 8345 up to this.

3. After I checked out last time my gmail reputation was very bad, IP reputation also seems to be bad.

Please tell us how to increase a bad IP reputation to High reputation in Gmail.

I hope you can help me this problem out.

Thank you.