Hello,
I have managed small debian 8.9 router with installed sendmail 8.14.4 from four months.The sendmail has tuned to use starttls with CA certificates without smtp autorization for mail client from internal network and for mail client from externel network they have ti has instaled certificates in mail client to use mail server and send mail. I thinked that everythink is ok until I found the follow problem . User from externel network can send email without certificate to user from my domain. Example my domain is pesho.net and mail client or script program with smtp tatata@pesho.net which is fake user from externel network can send mail to all my valid users from pesho.net exampes tatata@pesho.net to dian.gospodinov@pesho.net and so on.
What changes I have to do in my sendmail server that for users for externel network sendmail to want compulsory valid certificate
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