Looking at the languages used in Thunderbird source (https://wiki.mozilla.org/Tree_Rules/comm-central#Thunderbird):
$ cloc build/ ldap/ editor/ mailnews/ mail/
3938 text files.
3848 unique files.
949 files ignored.
github.com/AlDanial/cloc v 1.80 T=6.01 s (497.6 files/s, 127309.9 lines/s)
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Language files blank comment code
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C++ 360 36718 26562 207587
JavaScript 1098 39149 63692 195828
CSS 278 7371 2664 30455
C 83 5339 8278 29463
C/C++ Header 413 7091 8979 24034
IDL 238 3205 0 18852
XML 40 1365 690 16902
JSON 24 7 0 5367
DTD 180 772 1360 5344
Python 24 893 2422 3740
NAnt script 118 489 0 2512
Objective C++ 5 461 163 2231
HTML 62 178 22 1666
XHTML 14 186 98 1096
INI 28 46 12 687
Windows Module Definition 7 24 156 354
LESS 1 33 52 183
make 4 36 22 133
TOML 1 17 7 110
Freemarker Template 6 24 0 98
WiX source 1 11 25 71
Ant 1 6 5 49
Markdown 1 10 0 49
Bourne Shell 3 8 11 23
Windows Resource File 2 6 11 15
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SUM: 2992 103445 115231 546849
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