If you need an attachment from an archived email, be sure that you are either on the campus internal network or within Citrix to access the archived attachment. This will allow you to access the attachment in the original format.
The best way to deal with attachments is to have them within OneDrive and share them. This will not have to deal with downloading the document and then reuploading the document. This will allow one document to be edited without having multiple copies.
For more information on OneDrive: