Addressing an email using Thunderbird is not a difficult task, but there are several ways it can be done, with some differences from other mail programs. The most obvious change noticed by people migrating from Microsoft products is that Thunderbird places only one recipient into each addressing box, creating multiple addressing boxes when there are multiple recipients. This does not in any way affect the way the mail appears to the recipient; it is just the result of a layout choice that was made early in the Thunderbird design process.
To: The primary recipient(s) of this email
CC: (Carbon Copy) The secondary recipient(s) of this email. Recipients will see the email addresses of those in the To: and CC: field
BCC: (Blind Carbon Copy) Addresses in this field will have mail sent to them, but recipients won't know who was in the BCC: field i.e. those in the BCC: field will receive the email but those in the To: and CC: fields won't know who was in the BCC: field
If there is no entry in the To: field but only in the BCC: then the mail will be sent to all the BCC recipient(s) and the mail will be displayed to recipients as being sent to "undisclosed recipients" or similar wording by the receiving email program.
Google IMAP mail accounts will remove the names in the BCC list from your sent folder. As a result the sender – i.e. you – will have no record of to whom an email was BCCed. If you need a record of whom you BCCed in an email, you will have to manually record this yourself before sending the email. This is a feature only of Gmail.
Thunderbird does offer a Write option if you right-click a Contact in the list.
This is handy if you want to send just one mail, but rather useless if you have multiple people in mind to send the mail to. There is however a rarely used key combination supported by the operating system that allows you to select multiple entries in a list such as the one in the address book:
By holding down the CtrlCommand key you can select multiple entries, one per mouse click. Clicking on an entry in the list that is already selected will deselect that item.
In addition to this there is the ability to use the Shift key. Holding down the Shift key will select everything in the list between your mouse clicks.
Using a combination of Shift and CtrlCommand in the same action by changing the key held down at appropriate times you can make very efficient use of your time while fine tuning the selected list.
Whenever you click Write, Forward or Reply, Thunderbird opens a compose window. One of the features of the compose window is that it contains a Contacts Sidebar pane from which you can see all of the entries in your address book. This pane can be turned on and off using the key F9, or from the View menu in the compose window.
You can select entries from this pane simply by double-clicking, or by using the buttons at the bottom of the pane
or by right-clicking on the entries you have selected with your mouse or the Ctrl and Shift keys and then selecting a destination from the menu.
After you selected the add option, the addresses will be added to the list of recipients at the top of the mail, one line per recipient.
You may also drag and drop single Contacts or multiple selections of Contacts from the sidebar into any of the addressing boxes. Unlike the other methods described here, this will insert multiple Contacts into a single addressing box, but note that the Contacts will be parsed into the one-line-per-recipient format if you type Enter into the addressing box.
Type the email address directly into the relevant field at the top of the email. After you have typed a few characters Thunderbird will probably be able to auto-complete the entry for you by using your address books. Additional entry fields will be made available to enter addresses into when you press Enter.