They are in your system
1. Go to Address book and tools /export sent to a secure place or put on disk
Save it as two version
1. a WAB[Windows Address book] and then as a text file.
Favorites investigate your browser [W/Explorer FireFox] to save/export as a separate file.
In each case the change of ISP should not affect your E-mail Client or Browser -
Within the system Connection/Browser/E-mail client are 3 separate entities