Email deliverability is influenced by a lot of factors, including sender authentication, keeping clean email lists, sending wanted content, having a good sending reputation, and much more.

Your sending reputation is how ISPs identify you as a legitimate sender. Every time you send an email campaign, ISPs collect valuable data that says whether or not you follow proper sending practices.

There are two types of email reputation—IP reputation and domain reputation. Let’s take a look at the difference between the two and why paying attention to both is important.

IP Reputation

Email is sent from IP addresses, which serve as unique identifiers of email streams. Some companies send from a shared IP, which means multiple companies use the same IP address to send their email.

Senders with higher email sending volume usually opt to send from a dedicated IP address that belongs only to their organization. No matter what your sending volume is, most email senders should send their transactional and marketing email on separate IP addresses.

By using a dedicated IP, you can better control your IP reputation because you’re not impacted by other senders’ bad practices.

Check out this blog post to learn more about the differences between shared and dedicated IPs.

If you send your email from a dedicated IP address, it’s important to warm up the IP properly before sending to your entire lists. Check out our How to Warm Up an IP Address best practice guide to ensure you’ve set up and prepared your IP for your sending needs.

Domain Reputation

Your domain reputation is based on your sending domain instead of your IP address. This means that your brand takes precedence when it comes to ISP filtering decisions.

There has been a sharp move towards domain reputation predicated by the move from IPV4 networks to IPV6 networks. While it’s not yet common practice to use domain reputation, required under IPV6 (though Gmail is already the strongest proponent), ISPs are starting to use the combination of IP and domain reputation until IPV6 is fully adopted.

Portable reputation

The idea of “portable reputation” is very appealing to senders who want the flexibility to add new IPs, move IPs, or change email service providers (ESPs) without losing the good reputation they’ve already built from their sending activity.

Domain reputation also eliminates the need to warm up new IPs since ISPs use the reputation of the entire domain as their filtering metric. (With IP reputation, you lose all reputation history and data when you change IPs or ESPs.)

As a result, new protocols have been developed to help facilitate domain reputation as the next frontier for filtering.

Most importantly, with domain reputation, you can’t change an IP address to fix reputation problems.

Email sending mistakes can now affect your domain reputation and your brand in a bigger way than it ever has before. This is why it’s so important to have good sending practices.

To learn more about sending reputation and tips to stay in compliance with Internet Service Providers, download our 2019 Email Deliverability Guide.


As Twilio SendGrid's Sr. Director of Content, Jillian is responsible for ensuring that SendGrid provides valuable thought leadership content through the blog, whitepapers, webcasts, and more. When not writing and editing, you can find Jillian frequenting Denver restaurants in search of the best queso.