In Thunderbird, when you compose an email using the 'Write' window, the email address will be shown in 'FROM', 'TO' etc fields. It has to be included anyway. It is also helpful for the email address to be visible in cases where the contact may have more than one email address. So if you have assigned a 'Display' name then it will appear in this format: Display name <email address> The 'Display' name which is shown prior to the email address is based upon whether you have entered a 'Display' name for the contact in the Address Book. That 'Display' name can also be shown in the header area of the Message Pane and in the Thread Pane of received/sent emails if you have selected to use a 'Display' name. Otherwise, the display name that the sender included will be displayed or if no display name then the email address is shown. So, if showing the 'Display' name then you will not see the email address in those areas. To always use the 'Display' name you have assigned to the contact - which will override a name inserted by the sender: * Menu app con > Options * Select 'General' * scroll down to 'Reading & Display' section * select checkbox: 'show only display name for people in my address book'