Here are some Thunderbird 52.9 debs for Trusty amd64

thunderbird-dbg_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-dbgsym_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-dev-dbgsym_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-dev_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-globalmenu_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-gnome-support-dbg_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-gnome-support_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-af_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ar_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ast_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-be_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-bg_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-bn_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-br_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ca_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-cs_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-cy_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-da_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-de_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-dsb_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-el_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-en-gb_52.9.1+build3-0ubuntu0.14.04.1_all.deb
thunderbird-locale-en_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-es_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-et_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-eu_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-fr_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ga_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-gd_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-gl_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-he_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-hr_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-hsb_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-hu_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-hy_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-id_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-is_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-it_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ja_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ka_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-kab_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ko_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-lt_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-mk_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-nb_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-nn_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-pa_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-pl_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-pt_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-rm_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ro_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ru_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-si_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-sk_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-sl_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-sq_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-sr_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-sv_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-ta_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-tr_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-uk_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-vi_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-zh-hans_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-locale-zh-hant_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-mozsymbols_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird-testsuite_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
thunderbird_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
xul-ext-calendar-timezones_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
xul-ext-gdata-provider_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb
xul-ext-lightning_52.9.1+build3-0ubuntu0.14.04.1_amd64.deb