It can take a while, though.

And a lot depends on what you’re sending, how frequently, how large that list is, and what your company’s overall reputation is. One dedicated IP address might not be enough if you’re sending a million emails every day. No matter how good your reputation is.

In terms of sharing IPs with MailChimp’s other customers, I can tell you that it’s the very well known, larger brands that do the most damage. The “low budget, low experience” end of the market (as you describe them) sometimes make mistakes, but the damage is minimal because their lists are usually very tiny.

The most common mistake with small businesses is they’ll use an old list. And that’s just because they’ve never had the time to email those subscribers before. That’s usually the worst we’ve seen. They don’t have the budget to go buying lists, or doing those God forsaken “list appends.”

Medium and “big” businesses are more likely to “mix in” lots of different lists from their opt-in forms, CRMs, trade shows, online contests, list-appends, co-registrations, whitepaper download pages, etc.

And so yes, you’re right—they’re better off on a dedicated IP(s).

But for the opposite reason than you’d expect.

Very large, seemingly responsible customers with large lists can *sometimes* do more damage (inadvertantly or not) to the small businesses on our system than vice versa.

“From a sender reputation and delivery perspective, it is better to have a dedicated IP address for your use alone. You are protected from being punished for the actions of others.”

The problem I have with sharing an IP address with MailChimp customers is that you serve the low budget, low experience end of the market. That means I’m much more like to share an IP with people who (inadvertantly or not) impugn my reputation.

The thing is, by having a dedicated IP addres and being a consistent sender, my reputation can only go up. I can control my own destiny.

Conversely, by sharing an established IP with fly-by-night customers with small lists that may or may not be opt-in (and some may even be free) I’m in a situation where my reputation can only go down.

Until there is transparency from ESPs in terms of their IP scores and who you share that IP with, I’d rather have a dedicated address.