Improve Email Deliverability with Mailbox Provider Statistics from SendGrid

November 16, 2022
Written by
SendGrid Team
Opinions expressed by Twilio contributors are their own
Reviewed by
Ravleen Kaur
Opinions expressed by Twilio contributors are their own

Improve Email Deliverability with Mailbox Provider Statistics from SendGrid

Not all mailbox providers are created alike when handling incoming email. They can vary in their internal architecture, filtering methods, third-party blocking implementations, volume constraints, and geographical policies. With all these factors, truly understanding how to monitor or improve the health of your email program requires insight into the sending statistics for each mailbox provider you are sending to.  

Inbox placement by mailbox providers

Each mailbox provider from Gmail to Outlook to iCloud manages their recipient inbox placement differently, and they don't disclose precisely how they filter. Therefore, monitoring mailbox provider data is a very effective way to keep tabs on your deliverability. Whether you view them in the Twilio SendGrid console from the Mailbox Provider Stats, Mailbox Provider Comparison, or Deliverability Insights tabs, or if you retrieve the data through our stats APIs, regularly reviewing your email performance by mailbox provider is a critical part of maintaining strong deliverability.

Improved mailbox provider groupings

Twilio SendGrid has always grouped your email deliverability statistics by mailbox provider in its console. This allows you to easily see how your email deliverability performance measures at Yahoo compared to Microsoft, for example. The system also helps clean up this data by grouping mailbox providers together. A good example of this are the free Microsoft domains.,, and are distinct domains, but they are actually the same mailbox provider and use identical filtering logic. Grouping these domains together allows you to analyze your email deliverability statistics for all of the Microsoft domains in one place rather than having them separate. 

Today, we released an update to the current mailbox provider groupings, which makes Twilio SendGrid even more powerful. Specifically, we have added more independent mailbox providers to our list, increasing from 50 to almost 250 providers. Because of this update, far less data will be lumped into the “Other” bucket when you review your mailbox provider statistics. The new list of mailbox providers includes a much larger collection of global mailbox providers, which especially benefits customers who send mail to domains outside of North America. 

Twilio SendGrid now also distinguishes between entities like (B2C addresses) and G Suite/Google Workspace (B2B addresses), which were previously grouped together. This is important because G Suite and Gmail behave differently when it comes to spam filtering and inbox placement. A similar update is included for Microsoft domains. We now distinguish between Microsoft consumer domains, like or, from Microsoft business domains hosted by Office365. Distinguishing between B2B and B2C mailboxes at Google and Microsoft gives you a much more granular view of how your email program is performing, allowing you to compare two different audiences at two of the largest mailbox providers in the world.

We have also removed or consolidated several legacy mailbox providers from the list that either no longer exist or have been acquired by other providers. 

Before vs. after: mailbox provider statistics with Twilio SendGrid

This update is a positive change for users because it provides more detailed and accurate insight to specific mailbox stats. You may notice that your view in Mailbox Provider Stats has changed because we added additional mailbox providers and updated reporting guidelines. For example, you may see less traffic grouped as “Other” because we added additional mailbox providers. Or, your Gmail statistics declined after being separated into and G Suite/Google Workspace. This doesn’t mean your email deliverability has decreased – we are simply now showing how your emails are performing for B2C ( recipients versus B2B (G Suite) recipients.

We have also updated our naming conventions to closer align with the mailbox provider naming conventions. Previously, Microsoft statistics were found under the “Microsoft Outlook Live” label but will now appear under the more accurate “Microsoft Outlook” label. 

We understand that the increased granularity and reorganization of mailbox provider statistics may cause some initial confusion, but the goal of this change is to ultimately help you more effectively and accurately monitor email deliverability and sender performance. Check out your mailbox provider groupings today in your mailbox provider comparison tab in Deliverability Insights.

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