Hi,
I've uploaded new thunderbird packages here:
https://people.debian.org/~agx/icedove-lts/
Since this includes the switch to GTK+3 some more testing won't
hurt. Note that this likely won't be the final package since upstream is
looking into some gmail related fixes. Depending on when this will be
resolved I'll upload either 52.0 or 52.x. But the bulk of the changes is
in 52.0.
Cheers,
-- Guido