It looks like the ribbon has been customised so all the usual ribbon tabs are hidden and a new one called Home is the only one included. This customisation could be contained in the document itself or in the attached template.

Is this for all Word documents opened from your email package or just the one document? If you detach the document and then open it from a folder do you get the same issue?

It may be a 64bit version issue or your screen capture tool is dodgy but there are other oddities on your screenshot that may be somewhat related to the issue. There is an odd dropdown arrow under the paste button and above the tab type indicator - what does that do? The QAT is also hidden. Of other interest: The image for the paste button seems very pixelly. The dialog launchers have borders around them that I haven't seen before.

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Andrew Lockton
Chrysalis Design, Melbourne Australia