How to add a signature to your emails
DAMTP/DPMMS/Statslab webmail
Click Manage in the top menu bar, then Preferences, then the blue Compose tab. Type your signature into the box and click "Change for this and future sessions".
Thunderbird
Click on your email address at the top of the left-hand menu, then "View settings for this account". Either type your signature or tick the box to attach it from a file and browse for the file. Click OK to save your settings.
Pine and mutt
Create a file called .signature
in your home directory and pine and mutt will include it in your emails automatically.