IP gets blocked again and again

Hello!

I'm currently experiencing the situation that the IP of one of my servers (62.75.169.191) gets on your blacklist again and again. (that means that I place an investigation request and a few hours to days later the IP is removed and all queued mail get sent)

Again a few days later the mails are being blocked again and the server's IP is reported as "The host has been observed sending spam in a format that is similar to snow shoe spamming techniques."

Today I again submitted a removal request.

As I don't have any clue why the IP gets on the blacklist again, please advice what I can do to prevent that.
(the IP is not reported on any other blacklist)

Thanks in advance!

Best regards,

Daniel JM