Thunderbird won't install from Add/Remove Applications, so I tried sudo
apt-get install thunderbird, whereupon I was informed that IceDove had
replaced Thunderbird and the installation of IceDove proceeded forthwith
without incident.
Now I'm hunting for the Profiles location so I can start importing my old
profiles from the hard drive that housed debian before that computer died.
IceDove works on linux nearly exactly the way Thunderbird works on *indows,
so I can keep two IceDoves running in parallel on these two OS's (on
different computers) and transfer profiles w/o hassles if one gets hosed. I
had to do that once when an antivirus program made the Thunderbird Inbox on
the *indows PC vanish, and it went fine ... in the end, I restored the T-bird
Inbox perfectly.