if you do not want to see new mails do not check for them - no need to mangle messages
switch TB in the offline-mode or clsoe the mail-client based on WHAT will wahtever you think you need to implement dec ide "if the user is ready"
Sorry, but that's not what I meant. After reading a message, I would like to decide that this very specific message should disappear from my mailbox for some time (I'am not able to handle/answer this email today, so it should reappear tomorrow/next week/...).
I agree that this transforms email into a kind of todo/task-list. But many people I know are using email-accounts this way. Gmail and mailboxapp.com (and probably more) offer similar features, just google for 'snooze email'.
Very likely it is not necessary to modifiy Thunderbird (or any other email-client) for this. You just have to set up a filter folder 'do-not-show-until-time'>now().
Chris