Here is how to create persistent links to your gmail messages:
# gmail url from atom feed:
# turns into the following when you view it:
# both forms can be used as persistent urls.
To figure out the correct message_id (or th) to use, go to gmail in html view and read the link that points to your message.
This works even if you are not logged into gmail at the time, after asking for passwd etc. you are redirected to the correct message.
I should say correct conversation, these links bring up whole conversations. You can get the url pointing to an individual message in html view:
But I could not make this work in a persistent format yet...