Mimecast for Outlook - Proxy Servers

This article contains information on configuring and managing proxy settings for Mimecast for Outlook, including considerations for different network environments and recommended configurations to ensure proper functionality.

It is essential to review Mimecast for Outlook - Prerequisites before deploying Mimecast for Outlook.

Environment Considerations

When deploying Mimecast for Outlook into an environment where all access to the Internet is provided via a proxy server, you should consider the following:

• By default, Windows Proxy settings are assigned on a per-user basis.
• The Mimecast Services for Windows service performs all Mimecast for Outlook network communication. This runs as the NTAUTHORITY\Local System and not the logged-in user.
• By default, the Mimecast Services for Windows service routes to the internet based on the Windows Proxy settings. For example, if no proxy settings are configured, communication will be directed to the workstation's default gateway (primary route to the internet).
• Mimecast for Outlook communicates over an encrypted HTTPS connection, meaning that a standard Proxy server cannot perform any packet inspection.

Common Scenarios

Below are typical proxy implementations.

Internet Access via a Firewall

Internet access is provided via a standard firewall (or upstream proxy) where no Windows Settings are required. In this scenario, Mimecast for Outlook takes the direct route to the internet (to connect to Mimecast Services), and assuming there is no web filtering on the firewall or upstream Proxy level, there should be no connectivity issues. 

Internet Access via Corporate Proxy Server (No Authentication)

A corporate proxy server provides Internet access without direct access (Proxy Authentication is not required). In this scenario, proxy settings will likely be assigned per user via Group Policy. This policy will not influence Mimecast for Outlook communication as the Mimecast Services for Windows service runs as the NTAUTHORITY\Local System, not the logged-in user.

By default, Mimecast for Outlook will try to take the direct route to the internet (to connect to Mimecast Services). This communication will consequently fail, and Mimecast for Outlook will not function as there is no route available to Mimecast.

Customers with this network configuration should consider changing their Group Policy to apply Proxy Settings on a per-machine basis. Alternatively, users can configure the proxy server details using the Account Options menu.

• Laptop users will not necessarily require a proxy connection (e.g., when not in the office). To resolve this issue, users must edit the proxy settings in the Account Options box, disable the proxy server, and revert to the default system settings.
• Mobile users if the customer decides to assign per machine Proxy Settings. Users cannot use Mimecast for Outlook when there is no connectivity to the corporate Proxy.

Internet Access via Corporate Proxy Server (Authentication is Required)

Internet access is provided by a corporate proxy server, with no direct access available (Proxy Authentication is required). In this scenario, the behavior is the same as the point above.

Preferred Scenario

As Mimecast for Outlook is an application that utilizes a Cloud service, the preferred/recommended environment for Mimecast for Outlook to operate in is where there is a direct route from the client workstation to the Internet, or at least to Mimecast Services. This will ensure connectivity and Mimecast for Outlook functions as expected.

Proxy Settings

You can manually configure your proxy network settings. For example, if your company uses a proxy server, you may need to configure your proxy settings so your Mimecast for Outlook software can access Mimecast.

Proxy settings should only be adjusted if you have been explicitly instructed to do so by your IT administrators.

You can configure your proxy settings  in the Mimecast for Outlook client, by using the following steps:

1. Click on the  icon in the bottom left-hand corner.
   
   

   If the Mimecast for Outlook client isn't open, click the Mimecast ribbon and the Account Settings icon in the General section.

2. Click on the Proxy Settings menu item. The Options dialog is displayed.
3. Complete the fields as supplied by your IT administrators.
4. Click on Save.