First the 'shortcoming' of pre-packaged thunderbird:
You can not have two different thunderbird installs
You can, however, have two of these (portable installs):
Installing Thunderbird on Linux | Thunderbird Help
The important part:
Installing outside of a package manager
The installation file provided by Mozilla in .tar.bz2 format does not contain sources but pre-compiled binary files, therefore you can simply unpack and run them. There is no need to compile the program from source.
The following instructions will install Thunderbird into your home directory, and only the current user will be able to run it.
- Download Thunderbird from the Thunderbird download page to your home directory.
- Open a Terminal and go to your home directory:
cd ~- Extract the contents of the downloaded file:
tar xjf thunderbird-*.tar.bz2- Close Thunderbird if it's open.
- To start Thunderbird, run the thunderbird script in the thunderbird folder:
~/thunderbird/thunderbird
And in case of two different installs:
rename the ~/thunderbird to ~/thunderbird1
repeat step 1 to 5 for an other version
rename the new ~/thunderbird to ~/thunderbird2
This might work. I haven't tested it so all bets are off
but this is the way I would go if I wanted two different thunderbird installs.
The next part is also important :
http://kb.mozillazine.org/Run_multiple_copies_of_Thunderbird_at_the_same_time
a short quote from that webpage:
Making Thunderbird behave differently
Multiple instances of Thunderbird can be launched by starting Thunderbird with a -no-remote command line argument or by setting the environmental variable MOZ_NO_REMOTE=1 before you run any copy of Thunderbird. You must use a different profile to run each copy of Thunderbird, so if profile manager does not normally appear during startup then you will also need to specify -P on the command line. Multiple instances is intended for debugging, so use it at your own risk. (-no-remote first appears in version 2.0 via bug 325509. For earlier versions you must use MOZ_NO_REMOTE=1.)
with the -P option you can select a profile so both instances can have their own unique profile.
A profile includes accounts, settings, mailfolders etc. so this might work.
From the man page:
man thunderbird
OPTIONS
-P profile
If no profile is given to the -P op‐
tion, the profile manager will pop-up.
You will be allowed to create or select
a profile. Thunderbird then launches
with the selected profile.