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By Neil Anuskiewicz
If your deliverability numbers are consistently high, it probably means that your ESP is offering private IP addresses or does a good job of managing relationships with the major ISP’s. If the ESP is offering mostly shared IP addresses, high delivery rates mean that the company polices customers’ compliance with the CAN SPAM Act, a 2003 law designed to cut unsolicited mails. It also suggests that when shared IP addresses are invoked, the ESP is getting the situation straightened out relatively quickly. This is where good relationships with the ISPs are important.
What is an IP Address and Why Should I Care?
Every machine connected to the Internet has an IP address. The big difference between an IP address and, say, a cell phone number 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. Your family, friends and associates know it is you calling, and not some prank caller who happens to share your phone number.
There is no such guarantee with a shared IP address. Indeed, some ESP’s have customers share an IP address with thousands of others.
When you blast a marketing email, your messages are stamped as coming from a specific IP address—similar to how caller ID shows who is calling you. Your identity, however, is lumped together with everyone else who shares your IP address.
The bottom line is that ESPs are constantly battling to keep their pool of IP addresses in the good graces of the ISP’s, corporate networks and others. This is not a perfect system, however. While high quality ESP’s make sure their customers are CAN SPAM-compliant, recipients still file spam complaints. If a certain percentage of recipients file spam complaints (the precise level varies by the ISP or corporate network), the ISP or network administrator adds the IP address to a blacklist and blocks all email originating from that IP address.
The better ESP’s have relationships with the ISP’s and do a good job of keeping their IP addresses off blacklists. If the IP address indeed does end up on a blacklist, they are usually good at rectifying the situation.
If you opt for private IP addresses, follow recommended guidelines to avoid spam filters and stay CAN SPAM-compliant, your deliverability rates should be excellent.
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