Solution : https://service.sap.com/sap/support/notes/690055 (SAP Service marketplace login required)
Key words :
<head> <title>so_preview</title> <, so_sendinfo_display html templates, </head> tags, html format, html header, document view, document preview, recipient list, display notes, special characters
Related Notes :
| 792110 | SAPoffice: Characters displayed incorrectly in documents |