On 08/27/2015 07:29 AM, Alice Wonder wrote: > Maybe I'll start blocking any server with an SPF record that includes > more than 5 IP addresses, That's not a very good idea. major ESPs (eg: gmail.com) have way more IPs listed than that. > or servers where any host in the SPF record is in a DNS blacklist. That could work better, but I would still say be careful, you could certainly end up wih false positives doing this. Peter