The "m535_owningmutcode" value is the owner mailbox's mail code, while the "m535_exid" value is the Exchange mailbox's Exabyte ID.
Action: Post
Table: contacts
Payload
{
"firstname":"Young",
"lastname":"God",
"m535_owningmutcode" : "518920000",
"m535_exid" : "1214"
}
//509: 518920000
//526:518920000