Getting banned from linode for Spam complaints !!

Hello everyone,

We are a legitimate email marketers, we send 200 to 500k emails a day to our costumers but we can't inbox these few month our email are reaching the junk email Folder.

linode Cloud Hosting just closed my account cause they got a spam complain from some of our clients and they canceled my account, now i can't open an new account with them.

I figured all vps providers may do the same thing in case of spam complaints.

My question is :

Is there any way to prevent spam complaints from reaching the providers or to prevent the account from been canceled.

thanks you in advance;