First of all let’s clarify what an IP address is.  An IP address is a unique string of numbers separated by full stops that identifies a computer using the Internet Protocol to communicate over a network.

So what does this have to do with email marketing?  Well an IP address should be assigned to your email marketing account and this address will have a reputation that is monitored by various IP monitoring companies.  If you have a good reputation then your emails are more likely to make it to your subscriber’s inboxes.

But if a bunch of other clients are on the same IP address and their lists are not as clean as yours, they could result in hitting spam traps, have loads of complaints and being marked as junk.  So deliverability of your emails can be severely affected.  So you could be the best sender on the shared IP address and have the cleanest list out of the lot, but it would be completely irrelevant to the mailbox providers.

Let me break it down further with an example:

So even though you had 0 complaints, the overall complaint rate would be 20% (600 complaints out of 3,000 email senders), purely because you are placed on that shared IP address. The scary thing about this is that this percentage is actually high enough for mailbox providers to not only direct your emails to the spam folder, but to block your email from reaching the subscriber’s inbox altogether.

Another concern is that if you are compromised, then it’s really difficult to discover the exact cause of the deliverability issues. This is mainly due to the fact that you don’t know anything about the other senders on your shared IP.

If you had your own IP address any issues can be pinpointed to your account and worked on to resolve.  If you are working with a provider who does not offer this then it’s highly likely your access will be disabled until that IP reputation improves.