Modify Thunderbird so that it uses the correct SMTP server for your current network and IP. In other words, if you are at home, use your home ISP's SMTP, but if you use a school wireless network, switch to the school's SMTP. These various SMTP configurations should be manually controlled by the user, that is, you don't have to try and figure out which SMTP to use. Rather, it should be configurable in an options dialog.

Write a simple (i.e., nothing more than a simple "save session") extension to leverage the existing [http://developer.mozilla.org/en/docs/Session_restore_API Session Store API] in order to allow the user to save his/her currently open tabs and restore them. This is similar to what Firefox does when it unexpectedly crashes and gives the user the option to restore a previous session. NOTE: there are extensions that do this already, but many of them are more feature rich than need be. See also [http://www.beltzner.ca/mike/archives/2007/05/28/resurrect_your_session.html this blog post].