Thanks.
Actually, nullmailer is a message transfer agent, simply forwarding my
mail to the smtp at my provider. And nullmailer is authenticating with
my provider using a password. But it is not authenticating using STARTTLS.
But I will verify whether others are able to send email through my
nullmailer.
I'm not exactly sure what starttls is doing, perhaps some form of
encryption, but it seems that my issue is something new, caused by some
stricter authentication rules that spamhaus has decided are now
required, not something I changed on my side. Nullmailer has been
running for over a year and a half, and this issue just started.
Trouble is that I don't know how I can enable starttls on nullmailer,
nor how to replace nullmailer by exim, which I believe supports starttls.
On 2015-05-02 10:30, Bill Strosberg wrote:
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