Tinymail now integrates with GnomePasswordDialog and GNOME keyring. This means that it stores your passwords using the GNOME keyring service. (update, Evolution these days can also support gnome-keyring)/
The tinymail framework will only use this implementation if you use the gnome features in combination with the libtinymail-gnome-desktop platform library implementation. Other platform implementations of course need to implement getting and forgetting the password themselves. They can of course reuse or look at the code of the implementation for the GNOME desktop.
Note: Somebody please write the GNOME keyring API documentation. It’s almost undoable to understand what you need to do if you want to use the GNOME keyring service. It was even harder than using Camel. Oh and, while you’re at it, update the developers.gnome.org website so that the GnomePasswordDialog API reference documentation is also available online.