When you have a catch-all address you can set your #Thunderbird to answer from the adressed mail address in reploys.

e. g. someone writes you a mail adressing
bills1@yourdoma.in
then you reply
you willbe sending from
bills1@yourdoma.in

the setting is at the bottom and called "reply from this Identity when delivery headers match"
the regex will be "*@yourdoma.in"

thanks @jendrik