Licensing of the Outlook Add-In is controlled by the Client Access License (CAL) on the Mail Express server. The number of clients (Mail Express Outlook Add-Ins) allowed to connect at the same time depends on the number of CALs on the server. A single Mail Express Server can support up to 9999 CALs.
When the Mail Express Outlook Add-In connects to the server, it provides its IP address and host name, and is authenticated to the server. Each time the Add-In connects, the server provides it with a new lease. Once connected, the Add-In periodically refreshes its lease. After one hour of inactivity or when Outlook is closed, the lease is freed so that another Add-In can use it. If Outlook exits ungracefully (e.g., crashes or is forcibly terminated) or if the computer loses its connection to the network, the lease remains unavailable until it expires.
If a CAL is not available, a message informs you that a license is unavailable and a log entry is created. You can still send email with Outlook, but the email is not processed by the Mail Express Outlook Add-In until a license is available.
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