Matt posted a discussion of the portability of IP reputation over at his EmailKarma blog.
I have heard about Hotmail/MSN’s claim that if you add your new IPs to your SPF/SenderID record and send from your old IPs that your old IP reputation will transfer to your new IPs. I’ve not heard it working in practice, but it really can’t hurt to add your new IPs to your records as soon as you know what they are.
IP Reputation Portability
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IP reputation is not portable. That’s what domain authentication is supposed to fix. Hotmail’s description misses the point that once you have an authenticated domain, the reputation of individual ips no longer matters, only the reputation of the domain as a whole. Nothing needs to be “transferred”, it’s all the same entity.
The issue is that Microsoft has tied their hands by pushing SenderID, which only authenticates based on IP as presented in a SPF/SenderID record. It was a bad idea 3 years ago, it’s a bad idea now, and it results in questions about how to transfer reputation between IP addresses.
You and I both know that IP reputation is a stop gap, but rolling out the real domain authentication technology is taking a very long time.