1. If you choose Horde, click on the settings icon (the gear) at the top right corner, and then on Options and Mail.
2. In the Mail preferences, under General, select Personal Information.
3. Scroll down a bit, and you will find a place for your Signature. Note that you can use the default plain text signature, or create a personalized HTML signature that will be used when you write an HTML email.
1. If you choose RoundCube, locate and click on the Settings button (the gear).
2. Click on Identities, and select the identity linked to your email address.
3. You will find a field for your signature there.