eM client, Windows 7/Vista & Exchange

Dear All,

One of our clients is testing eM client with Microsoft Exchange 2016 server and Sophos XG firewall as MTA.
Within LAN everything is working just fine. They came into problem with access to Exchange from outside - users using laptops with Windows 10 are working OK, users using laptops with Windows 7/Vista cannot connect to Exchange server at all.

Thank you in advance for your help!

What is the error you are getting on the Windows 7/Vista eM Client installations? You can find the errors in Menu > Tools > Operations.