re : I went to "Options" , "General" and it appears to offer a place to enter the address of the start page, This means it shows a specific piece of information in the Message Pane on start up. When you start Thunderbird, it will open up on whatever folder you had last selected prior to exiting. So if you had selected the mail account 'Sent' folder and then exited Thunderbird, it would open displaying that folders contents when you next start. To write a new message, you click on 'Write' button to open a new 'Write' window. This has always been how thunderbird has always worked. Nothing has changed. re :'''Since T'bird has no "sent mail" button, like other email services''' It does not need one because it is an email client and not a different program eg: word processing type of program or image program etc that does not have it's own email and has to use the default email client on the computer. If you are using an entirely different program like MSWord or OpenOffice Writer etc and use the 'File' > 'Send' > document as email or similar, Thunderbird will open and so will a new Write message with the document attached ready for you to compose the email. So it sounds like you are confusing the difference between what you see when you open Thunderbird and what you see when you are using an entirely different program and want to send the document in an email that then auto opens Thunderbird with Write window pre opened.