E1 is part of the Enterprise family of Office 365 plans, which are built for larger businesses with concerns about security and compliance.

Considering the switch from an Office 365 Business plan? As a general rule, that makes sense if you need to accommodate more than 300 users. If not, Office 365 Business might meet your needs for now.

Note that Office 365 ProPlus technically falls under the Enterprise family of plans⁠—you can compare it to the others here⁠—but we don’t generally recommend it. You don’t get the collaborative platforms⁠, which are arguably essential.

I mention it because it’s the enterprise equivalent (not an exact match) of Office 365 Business. Similarly, you can think of E3 as the analog of Office 365 Business Premium, and of E5 in its own league with features that aren’t available with any Business subscription.

For Office 365 E1, its “matching” plan is Business Essentials—no desktop apps, but all the collaborative platforms.