One of our clients is about to turn on a spam filter that blocks all incoming @clientsite.com emails that don't originate from whitelisted IPs. "ping" says that cmail1.com and cmail5.com are both 188.8.131.52.
Are there any others I should hand over for them to whitelist?
And also, in case our B2B clients ask, what enterprise spam filter companies (Postini, for example) does Campaign Monitor work with to prevent being blacklisted?
You can check out our IP range here. You'll be pleased to know we consistently test our delivery through enterprise spam firewalls and all blacklists on a daily basis.
We're also releasing a tool in the next week or two that will make it very easy for you to test your campaign against all of the popular spam filters and gateways before sending your campaign.