I tried SeaMonkey too. Works fine for me. You don't have to remove firefox and thunderbird.
Download Seamonkey, unpack, create a directory seamonkey into your home-folder.
Install libstdc++5
Goto the donload-directory
./seamonkey-installer
Select a custom-install
Create an application-starter
Edit will start Composer.
I tried SeaMonkey too. Works fine for me. You don't have to remove firefox and thunderbird.
Download Seamonkey, unpack, create a directory seamonkey into your home-folder. installer
Install libstdc++5
Goto the donload-directory
./seamonkey-
Select a custom-install
Create an application-starter
Edit will start Composer.