Here you can see all ParticipationTypeMask Values below.
| Activity party type | Value | Description |
|---|---|---|
|
Sender- From
|
1
|
Specifies the sender.
|
|
ToRecipient – To
|
2
|
Specifies the recipient in the To field.
|
|
CCRecipient -CC
|
3
|
Specifies the recipient in the Cc field.
|
|
BccRecipient -BCC
|
4
|
Specifies the recipient in the Bcc field.
|
|
RequiredAttendee
|
5
|
Specifies a required attendee.
|
|
OptionalAttendee
|
6
|
Specifies an optional attendee.
|
|
Organizer
|
7
|
Specifies the activity organizer.
|
|
Regarding
|
8
|
Specifies the regarding item.
|
|
Owner
|
9
|
Specifies the activity owner.
|
|
Resource
|
10
|
Specifies a resource.
|
|
Customer
|
11
|
Specifies a customer.
|
|
Partner
|
12
|
Specifies a partner.
|
Polat Aydın - MSCRM Dynamics Blog 
Values after 4, where are they used in CRM?