Documents are not edited in Thunderbird. You use the correct program to perform that operation eg: Adobe Reader for a pdf document or Microsoft Word for docx or Excel for .xls or OpenOffice Writer for .odt files etc Any email you previously sent with a specific document will have that document containing info as correct at the time of attaching it. It has become part of the original email. If you have since updated that document in any way then I presume you have created an additional document of similar name in order to preserve the original. Mind you some people do just edit and save as it is but if overwriting the original it will mean loss of the original and you might not want to do that. That means the original email with previous attached document is not the same as the newly edited document, so you would need to attach the correct one. If trying to use a previously sent email because it would save you from entering all the contacts and also save you from typing all the content eg: right click on sent email and select 'Edit as new message'. Then you will need to remove any previous attached document and attach the correct updated document. If you are not using a previously 'sent' email: * click on '+ New Message' button to open a new Write window * Select the contacts that need to get email. * Enter a suitable Subject * Click on use the 'Attach' * select the correct document and click on 'Open' * It will get attached to email. * click on 'Send' You might find it just as quick to create an email with Subject, added email addresses and typed content BUT with no attachments and save it as a Template in the Templates folder. Then you can reuse the template repeatedly and just alter any specific data such as add new contacts or alter a bit of the content and of course attach the correct document. Not a lot different from using the sent 'edit as new message' - it just means you do not need to remove any previous inaccurate documents.