Negative Reputation Server - Please Help

Hi,

My server ip is 136.243.165.42 and has been "banned" with the reason below:

The IP address 136.243.165.42 was found to have a negative reputation. Reasons for this assessment include:
The host has been observed sending spam in a format that is similar to snow shoe spamming techniques.
To request that this IP address reputation be cleared, check the applicable boxes below and click Investigate.

We dont send spam emails. Can you help us please to find why our server is banned and we cant send emails to specific addresses?

Thanks