Selective relaying

[Harold Johanssen]

I have a sendmail server at home which I use for dealing with
emails from users in a domain of my own. I have configured it so that it
will only relay email from other PCs in my LAN at home, and from one or
two trusted external systems.

Now if I take a tablet or a laptop and connect to the Internet
using some WiFi hotspot goodness knows where, I won't be able to have any
emails sent from that laptop and from users in my domain correctly
relayed, unless I change the configuration of my sendmail server
accordingly specifically for the network that covers that hotspot. This
is of course not very practical, and also quite insecure.

Is there a solution for this? For example, could sendmail be
configured so that emails from specific users in my domain are always
relayed, no matter where they are coming from? This is also not
particularly secure, but it is easier to handle.

If not this, what other solutions, based on sendmail, could I
explore to tackle this problem?

[Lew Pitcher]

On Wednesday 08 May 2013 15:20, in comp.mail.sendmail, noe...@please.net
wrote:

Really insecure. Incredably insecure.

> If not this, what other solutions, based on sendmail, could I
> explore to tackle this problem?

You might use a VPN to place your laptop "inside" your network during it's
stays outside at WiFi hotspots.

Or, you might consider hosting a webmail solution for your roaming needs.
With IMAP between the webmail and sendmail, and SSL/TLS between the remote
device and the webmail, it would be a secure (albeit more cumbersome) route
to take.

--
Lew Pitcher
"In Skills, We Trust"

[David F. Skoll]

Harold Johanssen wrote:

> Is there a solution for this? For example, could sendmail be
> configured so that emails from specific users in my domain are always
> relayed, no matter where they are coming from? This is also not
> particularly secure, but it is easier to handle.

There are only two secure solutions:

1) Use a VPN so that IP-based relaying is secure.

2) Use SMTP AUTH and relay based on successful authentication.

Regards,

David.

[Claus Aßmann]

David F. Skoll wrote:

> There are only two secure solutions:

or more...

> 1) Use a VPN so that IP-based relaying is secure.
> 2) Use SMTP AUTH and relay based on successful authentication.

3) STARTTLS with a client cert.

cf/README

+----------+
| STARTTLS |
+----------+
....
Relaying
--------

SMTP STARTTLS can allow relaying for remote SMTP clients which have
successfully authenticated themselves. If the verification of the cert
.... [[ read on ]]] ...

[Andrzej Adam Filip]

IMHO all suggested solutions are valid but incomplete without abuse detectors
e.g. monitoring volumes of email sent with alarm and auto-block levels.

--
Andrzej A. Filip

[Harold Johanssen]

Thanks. SMTP AUTH is, in my case and for my needs, the simplest
solution.