Author: Adam D. Barratt Date: To: Andrew C Aitchison, Gary Dale CC: exim-users Subject: Re: [exim] sending e-mail through a directnic server
On Thu, 2019-11-28 at 14:00 +0000, Andrew C Aitchison via Exim-users
wrote: > On Thu, 28 Nov 2019, Gary Dale via Exim-users wrote: [...] > > It looks like the remote smarthost thinks I'm not using TLS.
>
> No. TLS is about encryption. The 1iaJ5F-00053v-JS log says that the
> remote smarthost thinks you are not *authenticating* (which should,
> but may or may not be, encrytped).
Given the configuration in the original mail, this is likely due to the
fact that mail.rossland.dental is a CNAME, and reverse DNS for the
eventual target resolves to "web152.dnchosting.com".
Debian's Exim packaging describes the use of the passwd.client file in
exim4-config-files(5), which in part says (with apologies for the
longish quote):
<quote>
Please note that target.mail.server.example is currently the value
that exim can read from reverse DNS: It first follows the host name of
the target system until it finds an IP address, and then looks up the
reverse DNS for that IP address to use the outcome of this query (or
the IP address itself should the query fail) as index into
/etc/exim4/passwd.client.
This goes inevitably wrong if the host name of the mail server is a
CNAME (a DNS alias), or the reverse lookup does not fit the forward
one.
Currently, you need to manually lookup all reverse DNS names for all IP
addresses that your SMTP server host name points to, for example by
using the host command.
You may minimize this trouble by using a wild card entry or
regular expressions, thus reducing the risk of divulging the password
to the wrong SMTP server while reducing the number of necessary
lines. For a deeper discussion, see the Debian BTS #244724.
</quote>
Thus, the hostname in passwd.client wants to be web152.dnchosting.com,
not mail.rossland.dental. (Or potentially a regex or wildcard if the
"152" is expected to change.)
