One of my key customers needs a new GNU/Linux installation and they are
willing to give GuixSD a try if Thunderbird is available.

I thought that's no problem and was surprised to not find anything
like Icedove in the guix repository.

I found two references on the net, but both are negative:

https://lists.gnu.org/archive/html/guix-devel/2017-08/msg00231.html
https://gitlab.secushare.org/infotropique/issues/issues/4

Are there any more recent news on the Thunderbird side? Does anyone have
more-or-less ready snippets available?

Maybe I can convince then to switch to an alternative: What would you
suggest for a graphical mail-reader that can import Thunderbird message
archives and address book and is part of Guix?

Thanks,

Björn