[exim] Deny send login name aliases

heloo
How to block send email from addrres loginname@??? , permit only send from alias login name eg.

file aliases

a.nowak: loginname
b.kowalski: loginnam2
....

send email only from a.nowak@??? b.kowalski@???
deny send from loginname@??? loginname2@???

thanks for the reply
regards
slawek