Why the header values after sending a mail is different from the one after fetching from the folders?

Question

When I send mail via graph client I get the headers like id, internetMessageId, subject etc. I store them for my purpose. If I send reply or forward for that mail using the header value id, I get the error Error Item not found. While tracing this, I came to know the id value immediately after sending is not the same as in the sent folder of my account. So after sending I additionally fetched the header by filtering with the internetmessage id got after sending. But in this case I get no response as it requires some delay to be stored in sent folder.