Solution : https://service.sap.com/sap/support/notes/788151 (SAP Service marketplace login required)
Key words : 
support package upgrade takes place, iis web site created, support pack stack, symptom mandatory steps, iis website created, \winnt\system32\regsvr32, <irj>\root\portalapps\, gw\external\exchange, prerequisites groupware connectivity, enterprise portal solution 1
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