Email synchronization with Outlook unsuccessful

[firehosp]

I have multiple email accounts from multiple clients and am having trouble syncing with outlook. I use the roundcube on the vesta panel. Can anyone guide me to configure this sync please? When I enter server and account information displays the following message. "we were enable to reache your email provider. please check your server settings. our try again latter"
Please help me so that I don't lose my clients. I'm new with the Vesta panel. Thank you very much in advance.