Best practice: sendmail and SMTP auth

Giorgos Keramidas keramida at
Thu Mar 13 02:04:56 UTC 2008

On 2008-03-12 14:19, Doug Poland <doug at> wrote:
> Hello,
> Not sure if this is the most appropriate place for this
> question, but since all my servers are FreeBSD 6.x/7.x, I'll
> give it a go...
> I am considering setting up SMTP auth on a number of sendmail
> instances that I control.  After much googling and reading, it
> is not clear to me that a server with SMTP auth
> configured/enabled can relay mail in both auth and non-auth
> modes.
> If one sendmail configuration cannot accommodate both SMTP auth
> and access.db, does one setup a dedicated SMTP auth host with a
> SMART_HOST option and feed incoming email to an non-auth
> instance of sendmail?

Sure it can.

One of the ways to do something like this is:

[1] Configure Sendmail to *require* authentication when one
    connects to its `submission' port (TCP port 587), and keep
    using /etc/mail/access for the default listener of the `smtp'
    port (TCP port 25).

[2] Then you can configure your `trusted' clients to connect
    through port 587, and let everyone else keep using port 25.

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