Maximize Deliverability Control with Shared IP Address Pool Improvements

April 06, 2023
Written by
Chelsea Coster
Opinions expressed by Twilio contributors are their own
Reviewed by
Ravleen Kaur
Opinions expressed by Twilio contributors are their own

Maximize Deliverability Control with Shared IP Address Pool Improvements

Mailbox providers monitor channels for email traffic to decide what is a reputable source of wanted mail, and what to filter out. If your business does not send enough email volume to successfully establish a sending pattern for mailbox providers to assess, then it’s best to send your email on a shared IP infrastructure with other similar senders. Twilio SendGrid administrates a shared IP pool infrastructure so our “Essentials” and “Free Package” customers can deliver their email programs through established channels. 

If you’re looking for more guidance on the topic of what shared IP addresses are and how they are different from dedicated IP addresses, please review our deep-dive here: Shared and Dedicated IPs: Which Should You Choose?

SendGrid has made some improvements to how we measure and group senders in our shared IP pool architecture. We are excited to share how this will maximize our customers’ ability to control their individual deliverability performance, and ultimately, improve the reach of their email program. While SendGrid has always grouped senders by reputation, we’ve recently applied a new sophisticated engagement quality algorithm to more dynamically and accurately group senders within our IP pool ecosystem. 

How mailbox providers view sender reputation

There are many factors considered by recipient mailbox providers such as Gmail, Yahoo, and Hotmail when assessing email sent to their users and determining whether or not the message should be routed to the inbox or quarantined as spam. These factors include:
  • Data quality
  • Email content
  • Sender history
  • Brand reputation
  • Sending infrastructure
  • Recipient reaction
Each of these factors incorporates numerous individual elements which are assessed by a mailbox provider every single time a request is made to deliver an email to a recipient. Within the email industry, the catch-all phrase for these factors is reputation

Each mailbox provider considers different aspects of a sender’s reputation to build their own view of whether the email being sent is wanted by the recipient. Importantly, mailbox providers require a certain level of sending volume in order to ascertain the reputation of a sender. To ensure a mailbox provider recognizes your reputation and rewards your sending practices, it is helpful to send on a network with other reputable senders.

How Twilio SendGrid assesses sender reputation

As an email infrastructure provider, SendGrid has advanced algorithms and systems that are continually evaluating sender performance based on how recipients interact with your email as well as mailbox provider feedback. After a yearlong data modeling project, we’ve discerned that we can more accurately approximate inbox placement by focusing on the following engagement quality dimensions.
  • Engagement recency: are you sending email to recipients who have recently opened or clicked?
  • Unique open rate: are your recipients opening your messages at a healthy rate?
  • Spam rate: are your messages generating excessive spam complaints from your recipients?
  • Bounce rate: are you attempting to send too many messages to addresses that don’t exist?
  • Bounce classification: are mailbox providers rejecting your messages due to a poor sender reputation or spammy email content?

Shared IP address pool placement

While we have always grouped senders by general reputation, our updated placement model focuses on grouping senders by engagement quality more specifically. This new model more consistently predicts deliverability outcomes, and it allows us to be more sensitive to risk within groupings if there is abuse. 

We have also automated our IP pool system to dynamically and responsively sort users based on their engagement quality. This means if you improve your sending habits to optimize engagement quality, you will automatically advance to sit adjacent to more performant customers within 24 hours. It also means if there is a sender in your pool that starts to underperform, within a day they will be automatically transitioned to a different pool, insulating your email program from risk.

Gain ownership over deliverability performance

By improving our reputation grouping, we are giving senders more ownership in maximizing their deliverability. Most senders should observe no significant change in deliverability performance with our new shared pool structure; in most cases, IP pool placement cannot compensate for or override an individual sender’s mailing habits. However, those who follow best practices and send wanted mail will be those with the best chance of achieving consistently strong performance. Senders can also feel confident that they are not sitting in a pool that is impacting their email program because of adjacent customer behavior.

Ready to take ownership of your deliverability? Follow our email best practices guide and the above suggestions to ensure that your email campaigns are primed for deliverability success from our new shared pool environment.  For more information on deliverability best practices, download our free Email Deliverability Guide – it contains everything you need to know about email metrics, reputation, and user experience.  And remember, SendGrid’s excellent Email Deliverability Services team is always available if you require additional assistance with your email program.

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