When these dialogs pop up, they deserve your attention - they don’t always indicate a problem, but they always indicate that you should examine the dialog, make an informed decision as to what to do, and if you’re not sure what to do, cancel the connection/sync.
The vast majority of the cases where these dialogs pop up do not have anything to do with our server - even when ‘omnigroup.com’ appears in the text at the top of the dialog. For example, in the screenshot here, ‘instant.arubanetworks.com’ has inserting themselves into the secure connection between the original posters’ Mac and our server.
There are legitimate reasons for something like this to happen, but there are also a number of nefarious reasons why someone might try to do this. We aren’t the party inserting ourselves into the connection, so it’s hard to say why it’s happening. By far the safest thing to do in cases like this are to simply hit the cancel button and try the sync again later.
That said, if you (or your IT staff) have sufficient experience reading dialogs like this to understand what it’s saying, and if what the dialog is saying to you indicates that the situation is benign, you can click the “Continue” button to proceed with the connection on a one-time basis. If you’ll be making connections from this location on a regular basis, checking the “Always trust” box and then clicking “Continue” will prevent the dialog from popping up in the future.
That all said, the most important thing to remember is this: if you are not sure what this dialog is telling you, the safest thing to do is to click Cancel and try your sync at a later time and/or from a different network.
Hope that helps!