I need two plug-ins for Thunderbird, you can bid for just one or both, up to you.
The first plug-in would allow you to make individual accounts on and offline, you should also be able to set specific times where thunderbird would log-in and be available for mlessages between.
The second plug-in would be similar to the wordpress plug in Deep Link Juggernaut. Basically you would create a list of keywords or phrases along with urls that they are linked to.
So, if I ever typed freelancer into an email, it would automatically create a link to freelancer.com.
Each key word or phrase could only be linked to one url.