First make sure that you have the correct Autodiscover CNAME DNS Record added with your DNS Hosting Provider. The record should look like autodiscover.yourdomainname with a value of exchangeauto.infoquest.com.
Are you being prompted for login credentials over and over in Outlook regardless if you're using the correct information?
First confirm you're using the correct login information by logging into Outlook Web App online via https://exchange.infoquest.com/. Once you've confirmed the information is 100% correct, open your PC's Control Panel > Credential Manager. Remove anything associated with infoquest.com by clicking the error to the right > Click Remove from Vault.
Are you using Outlook 2007 or older?
We recommend upgrading Outlook, Creating a new Profile, Setup account from Scratch. You can download Outlook through your customer control panel via https://cp.infoquest.com > Click Exchange Tab > Click the Display Name of the user in question > Click Download Outlook.
Are you receiving a notification that says "Allow this website to configure email address server settings? Your account was redirected to this website for settings. You should only allow settings from sources you know and trust."?
If you are receiving this notification, check the box "Don’t ask me about this website again" and then click allow. You must restart Outlook for this to take effect