http://www.mozilla.org/ports/os2/
June 17, 2004 Thunderbird 0.7 http://www.mozilla.org/products/thunderbird/
has been released.
"Thunderbird 0.7 is Mozilla's next generation e-mail client."
Zipfile:
http://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases/0.7/contrib/thunderbird-0.7-os2.zip
Installation instructions:
http://www.mozilla.org/products/thunderbird/releases/
Requires a libc0.5 based version of the GCC runtime library.
http://www.innotek.de/products/gccos2/download/gccos2download_e.html
Source: OS2VOICE