I have a VF page sending a meeting request:

<messaging:emailTemplate subject="Consumables Test Event" recipientType="Contact" relatedToType="JobContact__c"> <messaging:plainTextEmailBody > Dear {!recipient.Name}, Please attend the consumables test "{!relatedTo.CustomerEvent__r.Name}" for "{!relatedTo.CustomerEvent__r.Customer__r.Name}". Please answer by responding to this initation. </messaging:plainTextEmailBody> <messaging:attachment filename="meeting.ics" renderAs="text/calendar; charset=UTF-8; method=REQUEST"> BEGIN:VCALENDAR METHOD:REQUEST BEGIN:VEVENT UID:{!relatedTo.Id} <apex:outputText value="{0,date,yyyyMMdd'T'HHmmss'Z'}"> DTSTAMP:<apex:param value="{!NOW()}" /> </apex:outputText> <apex:outputText value="{0,date,yyyyMMdd'T'HHmmss'Z'}"> DTSTART:<apex:param value="{!relatedTo.CustomerEvent__r.EventStart__c}" /> </apex:outputText> <apex:outputText value="{0,date,yyyyMMdd'T'HHmmss'Z'}"> DTEND:<apex:param value="{!relatedTo.CustomerEvent__r.EventEnd__c}" /> </apex:outputText> SUMMARY:Consumables Test at {!relatedTo.CustomerEvent__r.Venue__r.Name} ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE; CN="{!recipient.name}":MAILTO:{!recipient.email} ORGANIZER;CN="Consumables Test":MAILTO:ourservice@5pxvocu476wr7aep8oclraf47.in.sandbox.salesforce.com LOCATION:{!relatedTo.CustomerEvent__r.Venue__r.Name}, {!relatedTo.CustomerEvent__r.Venue__r.PrimaryStreet__c},{!relatedTo.CustomerEvent__r.Venue__r.PrimaryCityDistrict__c},{!relatedTo.CustomerEvent__r.Venue__r.PrimaryCity__c} SEQUENCE:0 PRIORITY:5 END:VEVENT END:VCALENDAR </messaging:attachment> </messaging:emailTemplate>

I works great - the recipient sees a meeting request an may clickAaccept or Decline in Outlook. There is an email service setup to catch the reply: ourservice@5pxvocu476wr7aep8oclraf47.in.sandbox.salesforce.com

Question is, I cannot figure out how to catch the UID in the answer in order to update the attendee in question. I've looked at email header, attachement etc. but no luck. I am pretty sure that somewhere I'll be able to retrieve the original UID is the response.