Hello!

On Mon, Jun 03, 2019 at 10:16:20PM +0200, Marcus wrote:

> I try to use NGiNX 1.10.3-1+deb9u2 (Debian 9 version) as SMTP proxy in
> front of a postfix server. I defined one server that should accept
> encrypted connections only. Therefore I set "starttls only".
>
> But this server accepts plaintext mails also. If I use telnet to test
> the proxy it provides STARTTLS but I can relay a mail without using it.

Currently, "starttls" is only enforced for authentication, but not
for non-authenticated mail delivery, as with "smtp_auth none" in
your config. If you want to reject all non-encrypted
non-authenticated mail delivery, you can do so using an auth_http
script.

Recently discussed here:

http://mailman.nginx.org/pipermail/nginx-devel/2019-March/011970.html

--
Maxim Dounin
http://mdounin.ru/
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