How do I make it so sendmail (8.9.3) is capable of sending out mail but not receiving mail?? This is for the purpose of our web servers which should just have port 80 open, nothing else. All administration is done locally. We want to block all port 25 traffic but can't seem to do that without stopping outgoing mail.

Also, when it comes to our mail server, we are using sendmail 8.11.4, we would like to use it for outgoing mail but we have block this at this point. I can't seem to find any way to require any type of authentication before mail can be sent our. Is there a way, this allowing only registered personnel to send out mail??

Thank you.

You need to shutdown your POP3 server to stop recieving email.

Your sendmail daemon LISTENS on port 25 for INCOMING traffic. It does not need to be running for outgoing mail. Solution to your first problem, shut down sendmail.

Please clarify your second question.

There's no perfect way to make sendmail secure, unless you only allow users within your network to sendmail.

However, you can still install qpoper along with poprelay to allow other domains to send email. But they have to check email first, then sendemail. Check email process is like a login for them.

Thank you all for the help.

So let me get this straight, for sending mail using sendmail, the daemon doesn't have to be running, if so, that's great.

As for the second question, as I understand, in order to send mail remotely through port 25, you don't have to login or anything, how do we fix this so things are more secure??

Thanks :)

So let me get this straight, for sending mail using sendmail, the daemon doesn't have to be running, if so, that's great.
Correct, if you are sending directly from the server.


As for the second question, as I understand, in order to send mail remotely through port 25, you don't have to login or anything, how do we fix this so things are more secure??
Uh oh, if this is the case, you have an open relay. It won't be long before spammers start using your server as a relay. The default installaion of sendmail does not allow relay except for localhost. You have to explicitly turn this feature on, but DON'T. If you want to have password authentication for sending mail, visit sendmail.org and look into SMTP AUTH. You can also allow relaying from a specified block of IP addresses; this is usually what ISP's do.