An interesting thought, but I don't have enough knowledge to do all that in Sendmail, and the Exchange server is already up and running, so don't want to change from a product I'm familiar with to one I know relatively little about.

I understand moving out of comfort zone is tough. But I do not know if you can exclude just mail servers from authentication to send mails to exchange. Thats something I have never done or thought about.

Isn't there anyone out there who knows how to solve this simple problem? All I need is for sendmail to be the smtp server for people sending mail from their Outlook Express or Thunderbird. In MS Exchange this is really simple to do; I can't believe it's impossible with Sendmail!!

Hi there,

Linuxlover.chaitanya already mention that site you need: http://www.madboa.com/geek/sendmail-auth/
I checked it and only the subnetwork part missing in that document that you need.

The access(relay) file has to contain the subnetwork to authenticate the users in the local network.(local users)

Otherwise external users can use in outlook "This server use SMTP authentication" tab. (server ip address, login name, password tab need to be filled up)
That means you must forward out in your firewall the sendmail IP address and the users can authenticate against the sendmail server.

I already made this kind of configuration that you want with sendmail.
It was a gateway server for a internal exchange server.

The authentication in sendmail depends on the access file.

But if you will mix the internal/external authentication, the external users(laptop) will complain about the emails that sent out.
Obvious the exchange server wont contain them because they will authenticate against the sendmail. As well as you can't backup that emails either.

Might be a solution for that the pst file in outlook. But don't forget to "fine tuning" in outlook to syncronise the sent items too.

Laz.