David: >From what Spamhaus is saying it means you have an open relay - allowing systems external to your network the ability to send mail from your server without any authentication. Basically this means you are accepting connections to use your server as a "sender" of anything without making sure it is an authorized user. You can verify this by trying to send mail from your server using it's external IP address on port 25 without a username or password - if it relays your mail it will do so for anyone on the planet. This is the exact setup hunted by spammers to ply their trade. You can telnet to port 25 and see exactly what is going on. If you've been used as a spamming source you are also paying for a lot of packets that they are relaying through your server. There are thousands of tutorials on verifying email server setup - just identify which server software you are using (usually sendmail, postfix or exim), and Google "postfix telnet email test send". I haven't used nullmailer (whatever that is) I just invested the time and effort to get to know Postfix well - after about twenty years of fear and loathing of sendmail. If you are going to run an outbound email server, take the time to get to know the program. -- Bill On 15-05-02 07:51 AM, David Patte ₯ wrote: > Last year I decided to teach myself a bit about Linux and setup a > Linux server at home. It is being used as a webserver, as well as > having a c++ development toolchain. I also use it for developing > 'Meteor' apps. > > In the past month, I have realized that some blacklists have decided > to list my IP. Spamhaus suggests in its documentation that my outgoing > email is not correctly using SMTP Authentication. > > I suspect my problem is with nullmailer, and the fact that it does not > seem to support STARTTLS on ubuntu 12.04. > > Is there any way I can tell from email headers whether smtp > authentication was used in sending a particular email? > > Anyway, I am looking to hire a linux consultant, on an hourly basis, > to help me resolve this issue; and in the future, also help me setup a > few other unrelated tweaks on my server (such as running two versions > of PHP). > > Are there any ubuntu experts on this list available for occasional > hourly contract work? If so, feel free to contact me. > > David