"HTTP 400 - Bad Request" error when you open a shared mailbox in Outlook Web App in an Exchange Server 2010 environment Content provided by Microsoft Applies to: Exchange Server 2010 Service Pack 3Exchange Server 2010 EnterpriseExchange Server 2010 Standard Select Product Version All Products Symptoms Consider the following scenario:In a Microsoft Exchange Server 2010 environment, you create a shared mailbox whose SMTP address starts with "oma" (as in the name "omar," for example).You log on to Outlook Web App, and then you try to open the shared mailbox.In this scenario, the shared mailbox does not open, and you receive the following error message: HTTP 400 - Bad Request Cause This issue occurs because Exchange considers a URL that contains the "/owa/oma" string a request for a service. Resolution To resolve this issue, install the following update: 2961522 Update Rollup 7 for Exchange Server 2010 Service Pack 3 Status Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. Last Updated: Aug 26, 2014 Did this solve your problem? Yes No Tell us what we can do to improve the article Submit Thanks! Your feedback will help us improve the support experience.