You then send the email to your list but find that deliverability rates are lower than you
planned. This is mostly because none of your recipients at a major Internet Service
Provider (ISP) received your email. This is a disappointing outcome to say the least,
and you decide to look into the matter further in order to avoid low email delivery rates
in the future.

Why did this ISP block your emails? You learn that the ISP has blacklisted the IP
address that you share with numerous other customers of your Email Service Provider(ESP). Another email marketing customer sharing your IP address sent out an email blast and got too many spam complaints. As a result the ISP blacklisted the IP from which the email blast came. The problem is that this IP address is yours also.

Your email delivery rates were lower than normal because of the mistakes of another customer of your ESP's. This is obviously a caused by factor completely out of your control.

Problem and Solution

You may be surprised to learn that most ESP's have a very small pool of IP addresses that nearly all of their customers share. Consider requesting a private IP address from your current ESP (you may have to pay extra) or even switching to an ESP that offers a private IP as a standard feature.

Alternatively, if your deliverability numbers are consistently high, it probably means that
your ESP is already offering private IP addresses or they are doing a good job of
managing relationships with the major ISP's. If they offer mostly shared IP addresses,
good delivery rates mean they are doing a good job of insuring CAN SPAM compliance in their customers and-when your shared IP address blacklisting happens-they are able to get it removed relatively quickly.

What is an IP Address and Why Should I Care?

Every machine connected to the Internet has a unique number called an IP address. A
good analogy would be cell phone numbers.

The big difference is that you do not share your cell phone number with a large group of
people. You have a unique cell phone number through which people can reliably reach you and only you. They know it is you calling, and not some prank caller who happens to share your phone number.

With a shared IP address, you share your IP address with other customers of the ISP. With some ESP's, each customer shares an IP address with thousands of other customers.

When you send out an email campaign, your emails are stamped as coming from a specific IP address-similar to how caller ID shows who is calling you. It is kind of like "caller ID" for emails but you are lumped together with everyone else who shares your IP address.

The result of this situation is that ESP's are fighting a constant battle to keep their pool
of IP addresses in the good graces of the ISP's, corporate networks, etc. While high
quality ESP's make sure their customers are CAN SPAM compliant, recipients still can and will file spam complaints. If above a certain threshold of your recipients file spam complaints (it varies by the ISP or corporate network), the ISP or network administrator
adds the IP address to a blacklist and block all email originating from that IP address.

It is worth mentioning again that the better ESP's have relationships with the ISP's and
do a good job of keeping their IP addresses off the blacklists. If the IP address does get
blacklisted, they are usually fairly effective at getting the IP address removed from the
blacklist. This process does not always go smoothly though.

Watch Email Deliverability Like a Hawk

The important point to remember is that deliverability is key to email marketing success so watch your email deliverability like a hawk. Your ESP should provide reporting that makes this very easy

If your ESP is not performing for you then find out why and remedy the situation quickly. Try to make changes using your current ESP first. If nothing changes, then it might be time to consider a change.