$ echo "Jun 12 09 mail (sender@sender.com) - (recip1@domain.com) 0.075 9387
Jun 12 10 mail (sender@sender.com) - (recip1@domain.com),(recip2@domain.com) -1.889 25623" | perl -pe's/(?:\S+\s+){6}\K(.+)/($x=$1)=~tr,(),,d;$x/e'
Jun 12 09 mail (sender@sender.com) - recip1@domain.com 0.075 9387
Jun 12 10 mail (sender@sender.com) - recip1@domain.com,recip2@domain.com -1.889 25623