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Mailbox Provider Statistics

Mailbox providers – companies such as Gmail, Microsoft, and Yahoo – provide mailboxes to businesses and individual consumers, often with a wide assortment of domains available. For example, Microsoft allows individuals to select from the popular hotmail.com, outlook.com, and live.com domains when signing up for a webmail account. Despite the availability of these and other domains, the technology that Microsoft utilizes to make deliverability assessments, such as whether or not a message is spam, is the same at each domain.

While most of the large mailbox providers rely on the same basic principles to determine if mail is wanted, each has proprietary algorithms that make this assessment in a different manner, and it’s common for mailbox providers to reach separate conclusions when evaluating mail.

Therefore, it's incredibly important to monitor all of your primary deliverability metrics at the mailbox provider level – deliverability issues with one mailbox provider do not necessarily indicate problems with all the others, and grouping the individual domains by mailbox provider ensures that all domains are represented for each provider.

Monitoring at the provider level also helps you hone your solutions when problems do arise. For example, if your Gmail open rates suddenly drop, you may want to adjust your sending behavior to address your Gmail audience specifically rather than making sweeping changes across your entire email program.

Mailbox provider groupings

Within the Mailbox Provider Stats interface in the Twilio SendGrid App user interface (UI), individual domains are grouped together in order to give you the most accurate view of your deliverability performance across all domains at each provider.

For most senders in North America, the largest audiences will likely be for Gmail, Yahoo, and Microsoft. These are represented in the Mailbox Provider Stats view as “Gmail”, “Yahoo”, and “Microsoft Outlook,” and each grouping contains all the domains that are in use by each provider. For example, the "Microsoft Outlook" grouping includes statistics for hotmail.com, outlook.com, and live.com.

The Other Providers grouping

SendGrid offers the industry’s most complete list of mailbox provider groupings with more than 200 mailbox providers presented in Mailbox Provider Statistics. However, there are thousands of mailbox providers, and displaying them all as distinct items in the list of mailbox providers is untenable. Your statistics for mailbox providers that are not in our list will be captured in the “Other Providers” grouping. If you need more granular statistics or insights about these smaller providers, you should set up the Event Webhook, which allows you to consume, store, and organize your email statistics and event data however you like.

Important consumer mailbox providers

Below, you will find a list of the mailbox providers and the popular domains that are associated with each. When viewing mailbox provider statistics, you will likely prioritize these providers and domains.

Microsoft Outlook

  • hotmail.com
  • live.com
  • msn.com
  • outlook.com


  • yahoo.com
  • aol.com
  • verizon.net
  • ymail.com

Apple iCloud

  • icloud.com
  • me.com
  • mac.com


  • sbcglobal.net
  • att.net
  • bellsouth.net

United Online

  • juno.com
  • netzero.net
  • netzero.com

United Internet

  • web.de
  • gmx.net
  • gmx.com
  • mail.com


Cloudmark is a spam filtering company that protects hundreds of millions of mailboxes around the world. When it is possible to reliably determine that a mailbox provider is utilizing Cloudmark for spam filtering, we will group your statistics for those mailbox providers under Cloudmark.

  • cox.net
  • shaw.ca
  • mchsi.com

Vade Secure

  • earthlink.net
  • mindspring.com

Important B2B mailbox providers

B2B senders sending to a wide range of domains will likely find that the below list of mailbox providers constitute a large audience share, as these platforms are in use by companies of all sizes for inbound email solutions.

  • Microsoft 365
  • Google Apps
  • GoDaddy
  • Rackspace
  • Proofpoint
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