When I use webmail, my email messages are sent from a strange email address

With the Horde/IMP webmail program, you can control how your email messages are sent by setting up your Default Identity:

• Click Options
• Click Personal Information
• By default you will see the settings for your "Default identity."
• Enter any changes you would like (most importantly your from address)
• Optionally, you can also make new identities that will allow you to send mail from different email accounts. If you add more than one identity you'll get a drop-down every time you send me that will give you the option to choose from the identities you have created.