Hosting Outlook Web Access in an IFrame Is Not Supported
Microsoft Exchange Server 2007 will reach end of support on April 11, 2017. To stay supported, you will need to upgrade. For more information, see Resources to help you upgrade your Office 2007 servers and clients.
The Microsoft Office Outlook Web Access user interface cannot be hosted in an HTML IFrame. However, Outlook Web Access Web Parts can be hosted in an HTML IFrame. If Web Parts are hosted in an IFrame, users can click the Web Part link to access the Outlook Web Access user interface.
For more information about Outlook Web Access Web parts, see How to Use Outlook Web Access Web Parts.