Keep Outlook mailItem property (internet header) from being removed when forwarded/replied
问题 I'm trying to start up a thread of mails defined by the same ID (ID needs to be a specific value equal to the one in our database). I can assign a custom internet header just fine like this: sendMail.PropertyAccessor.SetProperty("http://schemas.microsoft.com/mapi/string/{00020386-0000-0000-C000-000000000046}/DCPID", taskId); Where the sendMail is an olMailItem and taskId is the id needed. When this mail is sent and recieved I can get my ID with the GetProperty method but when forwarded or