Earlier quoted context omitted.
this is because when an IP is blacklisted it's generally done in a contiguous block (subnet) that are probably shared by hosts on the same virtual lan (vlan). this is to prevent mailers from jumping to another ip on the same subnet. trunking an additional vlan into their virtual pool just for you would have constituted a major production change in probably 2 or 3 core switch layers. the operational risk and expenditu…
Interesting to know. I know nothing about the admin side of datacenters. It was a whole subnet that was blacklisted. That said, they offered me a new IP from a couple different subnets as replacement, so I don't think it was too hard for them to do it. They would let me have an extra IP, but wouldn't let me run the two IPs concurrently for more than 24 hours. This was especially frustrating since the subnet was black…
you got lucky though, most of the time the entire network of shared hosting providers is blacklisted from sending mail. they may have just rolled out a brand new subnet or something