In the world of email deliverability, technologies and methodologies are in a constant state of flux. ISPs have to be on the alert for new spam and virus attacks, and as a result are constantly changing their blocking and filtering technologies to combat these problems and to protect their customers. When it comes to delivering email to the Inbox, ISPs also have to be careful about what email they accept, especially regarding senders from which they have never seen email traffic.

A classic example of this is where a company may start with or switch to a different Email Service Provider, and as a result will be sending their email from a brand new IP address. From an ISP’s perspective, this is like “the new kid on the block” – they’ve never seen email traffic coming from this new IP address. They don’t know if these messages are legitimate or simply a spammer that has decided to switch IP addresses. Thus, they are going to be very cautious about the email coming from that new IP address, and will scrutinize it with the full extent of their spam filters until they can ascertain what kind of email is being sent and its impact on their network. If the messages sent generate complaints or high amounts of hard bounces, the ISP will most likely not remove these filters and may opt to bulk and/or block those messages altogether. However, if the messages don’t generate complaints, and are sent to valid email accounts, the ISP will most likely turn down their filters and let email pass through more easily. By the very nature of sending from a new IP address, the sender is building either a good or bad reputation with that ISP.

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