i mean the most important think in to to break the thread. is there any way to set the thread to the new email, builder. (Have stored that in my db so i know the values)
Gmail thread Id (X-GM-THRID) is assigned by the Gmail server. You can not assign it manually. You can of course get Gmail thread id using Mail.dll and search for it.
When grouping messages Gmail takes in to account several properties such as: - In-Reply-To header (assigned if you are using ReplyBuilder) - Similar subject ("Re: original subject", again assigned by ReplyBuilder) - Similar email body (original body, again assigned by ReplyBuilder)