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Sending Email Through Shared IPs vs. Private IP: Positives & Negatives

A frequent question we get is what the benefits are to sending email through a shared IP range vs. a private IP. Depending on the company and the situation, there can be positives and negatives, benefits and serious drawbacks if done incorrectly.

This post will aim to explain this subject and provide some much-needed knowledge when you’re talking to your email services provider of choice — regardless of whether it’s Dyn or not.

Terminology

Let’s get a few basic terms down if you’re new to the email game, using DynECT Email Delivery as a baseline.

Each Dyn MTA (Mail Transport Agent) is assigned a range of IP addresses. When you send email through our MTA, Internet Service Providers’ (ISPs) receiving mail servers will recognize those servers. Depending on their reputation, that mail can be flagged as valid, junk or spam.

Shared IP Range

A shared IP range means that when mail is deployed through Dyn, it could go through an IP or set of IPs that is shared with one or more other senders sending mail through those same IP addresses.

Private/Dedicated IP

With a private/dedicated IP or range of IPs, you will be the only sender having mail deployed through these IPs.  This will allow you to control your own destiny for a sending reputation and diagnose any issues should they arise with less variables.

Sending Frequency

Sending frequency is often the first criteria that will help define whether a shared or dedicated IP pool is better for your situation. You may experience poor deliverability if you’re not sending consistently from your IPs.  We look for a sender to have a minimum sending volume for a dedicated IP range to ensure they will have enough volume to maintain a sending reputation for their IP pool.

Since deliverability is often a game of ratios, the less amount of volume, the more damage a bad send can do to a sender’s reputation. The impact of an angry user flagging a message as spam on a send of 10,000 as opposed to a shared pool of millions and millions is noticeable.  You’ve heard of the phrase “A bad apple spoils the bunch”? Think of a spam message as that bad apple and the impact of it in a bushel as opposed to an entire orchard. It’s not great, but when you’ve got a ton of other great red apples, the impact is lessened.

If you send too much email too fast to an ISP, they might mark your email as bulk or outright reject it. If you send too little or too infrequently from that IP, the same can happen. By delivering with other reputable senders, it keeps the volume high enough so the IPs are noticed as an outgoing MTA with the other marketers’ mail filling in the volume for a more consistent flow.

If you’re simply sending on your own and don’t have enough volume, your errors or best practices oversights are going to stand out even more, whereas they might be glossed over by the traffic of other senders and be much more forgiving.

As time has passed, ISPs are able to more accurately track reputation by the actual sender than by the IP. As a result, you get some benefits of sending off a shared IP range, but your own reputation still builds for your sending domain.

Warming Up

The process of warming up an IP is fairly simple. As users continue to send through our shared IP range, those various IPs continue to get great reputations for all the clean sends we do. If a client qualifies for their own IP address, we’ll assign one and place it in the pool for several weeks. At the point we feel it’s ready for the client, we’ll make the configuration changes and move that traffic accordingly. The risk of moving them over to a “cold” IP is they’ll lose any sending reputation they built up and it will take that much longer to rebuild it.

When would a private IP make sense?

There are plenty of cases where sending through a private IP is the right option and depending on your sending volume, multiple private IP pools sometimes may be the best choice.  We work with our clients at Dyn to understand their sending habits, desires and priority for various mail types and can segregate the sending to private or shared IP pools to optimize deliverability.

Many senders have mail from at least two main categories: transactional and marketing.  Transactional mail is often a priority and needs a quick delivery time so that the end recipient is not waiting for an important piece of transactional mail.  The marketing category of mail needs to be reviewed for list cleaning practices, engagement rates and more before a suggestion of private or shared IP pools can be made.

These are the types of topics that our mail team thinks about all the time. If you have questions about any of this, please reach out and if you’re interested in trying one of our six email options, take a look at our email section or contact Enterprise Sales.


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Whois: Stephen Wheeler

Stephen Wheeler is the Director of Deliverability for Dyn, the world leader in Internet Performance Solutions that delivers traffic management, message management, and performance assurance. Follow on Twitter: @InboxExpert and @Dyn.