Command 'groups' doesn't show group membership correctly
# display the groups user 'dovecot' is in
dovecot : dovecot mail
# as shown, user 'dovecot' is in group 'dovecot and group 'mail'
# display the group user 'mail' is in
mail : mail
# as shown, user 'mail' is in group 'mail'
# check who are the members of group 'mail' and I should see user 'dovecot' and user 'mail'
$cat /etc/group |grep mail
# however, I only see user 'dovecot' here
Is there a reason why user 'mail' is not shown as a member of group 'mail' in the last command?