Problem

When the MailGate Secure Collaboration Add-in 2.2.1 for Outlook is installed on Windows 10
it is possible to encounter an issue where the Add-in won't connect to the MailGate server
when TLSv1.0 is disabled under Administration, Network Settings, Security, although TLSv1.1 and TLSv1.2 are supported on both the server and the Add-in application. The most common scenario is when the customer' security team requests so, or say after a vulnerability scan.

In those occasions where the Add-in log shows:

ERROR: REST: ERROR: IRestRequest: Method: GET; Resource: auth/globalSettings
IRestResponse: Uri: ; Status: Error; Content: The request was aborted: Could not create SSL/TLS secure channel. at Axway.MG.Client.MailGateClient.handleGetResponse[T](IRestRequest request, IRestResponse& response, WebResponse& webResponse)

There could be couple reasons for that (assuming Firewall and or other network devices are not the cause)

Resolution

1) The first thing to make sure is that the Add-in is installed from Setup.exe
and not from SecureCollaborationOutlookAddinSetup.msi package.
That is because Setup.exe contains the necessary .Net 4.6.1 version which is necessary for the Add-in to function
and resolves this dependency even when newer .Net versions are installed.

2) Check if .Net framework is configured to use upper protocols on the workstation where the Add-in operates
by examining the Windows registries for Net Framework

set strong cryptography on 64 bit .Net Framework (version 4 and above)

HKLM:\SOFTWARE\Wow6432Node\Microsoft\.NetFramework\v4.0.30319' DWord named 'SchUseStrongCrypto' -Value should be set to '1'

set strong cryptography on 32 bit .Net Framework (version 4 and above)

HKLM:\SOFTWARE\Microsoft\.NetFramework\v4.0.30319' DWord named 'SchUseStrongCrypto' -Value should be set to '1'

If the above parameter is with value 0, you could change the value to 1
and then restart Outlook (which would also restart the Add-in) for the change to become effective.