I do not think that means what you think it means

Yesterday, I looked at the analysis of ESP delivery done by Mr. Geake. Today we’ll look at some of his conclusions.
“Being blacklisted most likely suggests that sender IP either sends out to a great deal of unknown or angry recipients.” That’s not how most blocklists work. Most blocklists are driven by spam traps or by the personal mailboxes of the list maintainers. The only blocklist that took requests from the public was the old MAPS RBL, and I don’t believe that is the case any longer.
Blocking at ISPs is often a sign of sending out a lot of mail to unknown or angry / unengaged recipients. But most ISPs don’t make their lists public. Some allow anyone to look up IP addresses, and if we had the IPs we could check. But we don’t, so we can’t.
“[…] if you share this IP with Phones4U then only 62% of your emails will be accepted by a recipient’s email server. That’s before they hit the junk filter. I wouldn’t want to pay for that.” This conclusion relies on the Sender Score “accepted rate” number. Accepted Rate is a figure I don’t rely on for much. I’ve never been able to reconcile this number with what client logs tell me about accepted rate. For instance, I have one IP address that has a 4.4% acceptance rate. But I know that 19 out of 20 emails from this IP do not bounce. In fact, it’s rare to see any mail from this IP bounce.
The one thing that Mr. Geake gets right, in all of this, is that if you’re on a shared IP address with a poor sender, then you share that sender’s reputation. Their reputation can hurt your delivery.
But a dedicated IP isn’t always your best bet, either.  Smaller senders may not have the volume or frequency required to develop and keep a good reputation on an static IP. In these cases, sharing an IP address with similar senders may actually increase delivery.
For some senders outsourcing the email expertise is a better use of resources than dedicating a person to managing email delivery. For other senders, bringing mail in house and investing in staff to manage email marketing is better.
Tomorrow: how do you really evaluate an ESP?