Run Test E-mail AutoConfiguration to confirm Autodiscover is resolving to Intermedia servers which helps Outlook to connect properly. If Outlook shows Disconnected at the bottom of the status bar, this issue may occur due to improper Autodiscover resolution. ost file may grow in size and end up being corrupted constantly. To do this open Outlook and navigate to File > Account Settings > Account Settings > double-click on the Exchange mailbox > More settings > Advanced tab > uncheck Download shared folders > save changes > restart Outlook and test the behavior.

If a user has Full Access to several mailboxes, it is recommended to uncheck “Download Shared Folders” setting in Outlook running in Cached mode. Note: To avoid re-occurrence of the issue, you may need to reorganize your mailbox so that folders contain no more than 5000 items each as recommended in How To Organize A Large Mailbox. You can delete and recreate the OST file. Read the Support Center article on How To Create, Compact, Repair Or Delete Offline Folders (How To Rebuild OST File) for instructions. If there is an improvement in Outlook performance in Online Mode, it means the Outlook local cache file (.OST) is corrupted. Read the Support Center article on How To Enable Cached Exchange Mode In Outlook for more information. Run Outlook in Online Mode: go to File (Tools) > Account Settings > double-click on Exchange email address > uncheck Use Cached Exchange Mode > save the changes > restart Outlook.

If the Outlook status is Working Offline, open the Send/Receive tab and disable Work Offline option. Sometimes Outlook may go to Work Offline status when there are intermittent issues with the Internet connection

Microsoft outlook not responding issues