You cannot send mail in Outlook with BPOS account connected. Mail items stuck in the Outlook Outbox folder. Other symptoms that you may experience:
The issue results from the disconnection between your corporate network and BPOS. It may indicates that there is network communication issues with you internet connection which triggers the connection timeout unexpected.
As a workaround, you may check how it works if increasing the timeout value to 60s (30s by default) with the steps following: