I'm going to config my sendmail server . When reading the document , I knew that the /etc/mail/relay-domains file is contain all domain that my mail server could relay to . But I would like to send to whatever domain I want and adding all of them to that file is so not comfortable .
So how should I do ? ( adding 0.0.0.0 to that file or adding 0.0.0.0 to /etc/mail/access ) .
Thank for reading

Don't EVER make your mail server as open relay!!!! Your mailserver will get blacklisted.

Suppose your mailserver is B. If A tries to send a mail to C using B, sendmail will deny the request by default to prevent spam. If you want to allow some domains to do that then configure relay-domains file or access file.
A better way is to use mailserver authentication to free you from adding and removing domains.



If a user on B tries to send a mail outside then no problem. No config needed.

If A tries to send a mail to a user on B then also no problem. No config needed.

yes ofcause I do not want to be in the blacklisted . But you know , I would like to make smtp must authenticate , and a people who could authenticate success could sendmail everywhere he want .

I think that is the better way , because as the administrator , you could not tell the client that which domain he could send to and which not .

So , thank you for answering my question , I've been wating this answer for long time , and , if you have any idea more about it , give me some of your experience.

hey , I forgot my purpose !

Back to the thead , how to make sendmail could send to everywhere I want ?

You need to have your domain set (and only your domain) for relaying. This will take care of your problem. Do not set any other domain to be relayed and you should be alright.