Please use download.mozilla.org to retrieve the latest Thunderbird release. 

For example, if you wish to download the US English installer for Windows (32bit)
the url is
   https://download.mozilla.org/?product=thunderbird-latest&os=win&lang=en-US

This could be pasted into the location bar of a browser, or used with curl or wget,  e.g. 
wget -O ThunderbirdSetup.exe "https://download.mozilla.org/?product=thunderbird-latest&os=win&lang=en-US"

For other operating systems replace 'os=win' with:
   OS X                       os=osx
   Linux x86_64               os=linux64
   Linux i686                 os=linux

For other languages replace 'lang=en-US' with:
   Albanian                   lang=sq
   Arabic                     lang=ar
   Armenian                   lang=hy-AM
   Asturian                   lang=ast
   Basque                     lang=eu
   Belarusian                 lang=be
   Bengali (Bangladesh)       lang=bn-BD
   Breton                     lang=br
   Bulgarian                  lang=bg
   Catalan                    lang=ca
   Chinese (Simplified)       lang=zh-CN
   Chinese (Traditional)      lang=zh-TW
   Croatian                   lang=hr
   Czech                      lang=cs
   Danish                     lang=da
   Dutch                      lang=nl
   English (British)          lang=en-GB
   Estonian                   lang=et
   Finnish                    lang=fi
   French                     lang=fr
   Frisian                    lang=fy-NL
   Gaelic (Scotland)          lang=gd
   Galician                   lang=gl
   German                     lang=de
   Greek                      lang=el
   Hebrew                     lang=he
   Hungarian                  lang=hu
   Icelandic                  lang=is
   Indonesian                 lang=id
   Irish                      lang=ga-IE
   Italian                    lang=it
   Korean                     lang=ko
   Lithuanian                 lang=lt
   Lower Sorbian              lang=dsb
   Norwegian (Bokmål)         lang=nb-NO
   Norwegian (Nynorsk)        lang=nn-NO
   Polish                     lang=pl
   Portuguese (Brazilian)     lang=pt-BR
   Portuguese (Portugal)      lang=pt-PT
   Punjabi (India)            lang=pa-IN
   Romanian                   lang=ro
   Romansh                    lang=rm
   Russian                    lang=ru
   Serbian                    lang=sr
   Sinhala                    lang=si
   Slovak                     lang=sk
   Slovenian                  lang=sl
   Spanish (Argentina)        lang=es-AR
   Spanish (Spain)            lang=es-ES
   Swedish                    lang=sv-SE
   Tamil (Sri Lanka)          lang=ta-LK
   Turkish                    lang=tr
   Ukrainian                  lang=uk
   Upper Sorbian              lang=hsb
   Vietnamese                 lang=vi
   Welsh                      lang=cy


Mozilla Release Engineering
Email: release-engineering@lists.mozilla.org
Web:   https://groups.google.com/forum/#!forum/mozilla.release.engineering