''re :revert back to Firefox 101, which I believe was presented in the mass update of 102. '' Thunderbird has nothing to do with the browser called Firefox. The current release for the browser is 105.0.3 and just in case you meant Thunderbird - there was no Thunderbird 101 '''re :a: Address lists could not be easily selected to send emails to .''' Not sure what method you are using but nothing has changed if you use the 'Contacts Sidebar' * In 'Write' window where you compose email, enable the 'Contacts Sidebar' ('View' > 'Contacts Sidebar') * Select the name of the address book which contains the Mailing List It then lists all the contacts in that address book including the names of any Mailing Lists. * select the mailing list name * click on eg: 'Add to Bcc' The name of the Mailing List is auto added to Bcc. Perhaps you do not want to use the mailing list name, which is less usual because you have put them in a Mailing list - maybe for some reason you want to see all the contacts individually and you only have a small list or want to remove a particular contact This method does involve more moves than simply adding via Contacts Sidebar and it must be done via the Address Book. In Address Book * Select the 'Mailing List' name * click on first name in list, then press Shift and click on last name '''OR''' quick method Use 'Ctrl+A' to highlight all names This highlights all the contacts. * Click on 'Write' Write window opens listing all the selected names. All the names will get auto put into the 'TO' field. But perhaps you want them all in the 'Bcc' field. * Make sure the mouse curser is in the TO field at the end of list of names. * Use 'Ctrl+A' to highlight all names OR right click on a selected name to see drop down menu and choose 'Select all addresses in TO' * Right click on highlighted names and choose 'Move to Bcc' All contacts previously in 'TO' field are auto put into a Bcc field - note you do not have to open the Bcc field first. The right click on an email address whether it is in a TO, Cc or Bcc will offer many options for moving etc. '''re :b. no check boxes for sending such as "TO", "CC", "BCC".''' The very old method of having one contact per line and individual checkboxes which take longer to select was removed a long time ago. The current format was introduced back in version 78 and it is more versatile. I discovered it was also much quicker once I'd worked through some options. Now, there is only one section for TO and likewise for Cc and Bcc. Each section can hold as many email addresses as you require. The TO field is auto enabled. You can manually choose to open the Cc and or Bcc by clicking on the respective buttons which are located to the right of the 'From' . If using the 'Contacts Sidebar' then you can select contacts and drag them into a pre opened eg: Cc field OR you can use the 'Add to Cc' etc buttons and it will auto open whatever you selected and put all selected contacts into that field. Perhaps this Article may help you. https://support.mozilla.org/en-US/kb/addressing-email