Yes! You can use ExtendSync with multiple personal mailboxes, as long as each mailbox meets the licensing and setup requirements.
ExtendSync supports users who need to work across different Microsoft 365 (M365) profiles within the same tenant.
Prerequisites
Before using ExtendSync across multiple mailboxes, ensure the following:
ExtendSync License for Each Personal Mailbox
Every mailbox that will use the ExtendSync add-in must have its own license assigned in the CloudExtend Subscription Portal.
NetSuite Prerequisites
Each user profile must meet NetSuite access and permission requirements.
This includes role configuration, token permissions, and other NetSuite prerequisites.Core Setup + Feature Enablement
Autopilot, Send from Outlook, file handling settings, and other ExtendSync features must be enabled per mailbox as needed.
➡️ See the full prerequisites guide here
How to Use ExtendSync with Multiple Microsoft Mailboxes
ExtendSync identifies your login via your Microsoft 365 (M365) account.
Because of this, there are two ways to use ExtendSync with multiple personal mailboxes:
Option 1: Open Each Mailbox in a Separate Outlook Profile
Example Setup:
Microsoft Profile 1 → Open in Outlook Desktop
Microsoft Profile 2 → Open in Outlook Web (OWA)
ExtendSync will recognize the M365 account for each profile.
This allows you to use both ExtendSync add-ins simultaneously without needing to sign in and out.
Option 2: Use One Outlook App at a Time (Requires Switching Profiles)
If you prefer to use only Outlook Desktop (or only Outlook Web):
You must:
Sign out of the current mailbox
Sign in with the other Microsoft profile you want to use
Reopen ExtendSync in that mailbox
ExtendSync will then authenticate to the mailbox currently in use.
💡 This method works, but switching profiles frequently is less convenient.
Use Option 1 if you need simultaneous mailbox access.