re :''Why does <return> after one e-mail address NOT open a new field of the same kind for additional addresses as it was in former versions?'' Because it has been redesigned :) If you want to send to two people in a TO field then you type two email addresses one after the other. All is well explained at this link and I found that after reading it, I soon got the hang of things and it's quite easy. https://support.mozilla.org/en-US/kb/addressing-email