It is always a good idea to have a least one email address in a 'TO' field even if it is your own, assuming you are going to have all the others in a BCc field. Some servers can think you are sending Spam if the TO field is not used at all. I'm not sure how you send out group emails, but here are some suggestions for you to consider. The bottom line is you should always check all details prior to sending. Some people simply create the email and manually add each contact in either TO, Cc or Bcc fields. Rather time consuming and more easy to make errors. Some people use the 'List' option in 'Address Book' to create specific lists for group emailing. There are two available methods for using the List in a new message eg: Bcc field. Good Info on Mailing List: * https://support.mozilla.org/en-US/kb/how-create-and-use-mailing-lists-thunderbird Standard way of selecting a list and knowing all will be using a Bcc. In a new Write message. * Enable the 'Contacts Sidebar' * select the 'address book' which holds the List. * select the 'List' name and click on 'Addto Bcc' button See images below as guide. Another option: Create a template email. * Click on 'Write' * Enter Your email address in a TO field * Enter A List/group added in a 'Bcc' field' * Enter Subject : enter subject * If you use basic info each time, then type this as well * Save as a template in Templates folder. Next time you want to send email to that group/list. * Click on 'Templates' folder * double click on the relevant email to open in a new Write message. * Check/Edit message as required. * Send. Another option: There is an addon which you could use called 'Mail Merge' This can use a .csv file or address book (not list). So in this case you would create a special 'Address Book' to act as a group. You create a template email which is used to do Mail Merge. You create special fields which will be auto filled by mail merge. This addon then sends one email separately to each person, so this does not need bcc as each email will use a TO field but only to the one person. It means you can personalise each email. * https://addons.mozilla.org/en-GB/thunderbird/addon/mail-merge/ Another option: Note: this addon can be used in version 57, but will not be maintained beyond that. * https://addons.mozilla.org/en-GB/thunderbird/addon/use-bcc-instead/ I've not used this addon, so cannot really comment on it. Please read the info carefully to ensure it really offers what you are looking for, but bare in mind it will not be maintained to work in TB 60.