Notes/Domino 6 and 7 Forum : RE: Blocking spoofed messages from internal SMTP users

Hi Rupert

Thanks for your response - the problem is that I dont want users to be able to send smtp mail other than via NOTES or they must authenticate to send OUTGOING SMTP Mail - authentication only works on incoming SMTP mail.

One of the restrictions set in the configuration document specifies hosts must be on the internal domain the correect host name ie lets say I work for ACME with a domian name of ACME.com I can restrict who can send SMTP Mail to that specific domain name.
So I cant impersonate BillClinto@whitehouse.gov but I can do the following :-

FBloggs@ACME.com decides he is going to spoof his bosses email address ie BSmith@ACME he can by simpy setting his outlook account to point to the SMTP Server running the SMTP Listener facility and send an email to anyone under the name of BSmith@acme.com.

One solution is to rightly place the outgoing SMTP Server in the DMZ and inhibit the firewall to prevent users from directly accessing this server to relay SMTP mail.
Another way is to switch the listener off however for small companies (which we are not) probably have their incoming and outgoing mail on the one server.

There must be a way to ensure that Bill Smith@acme.com is actually the user sending the email - Domino only allows authenication of incoming SMTP from servers not outgoing SMTP from users.

I will investigate further the option you suggested "Only allow connections from connections with the following IP Addresses" using the IP addresses of all the Domino Servers that will route mail to the SMTP Server then hopefully preventing users from relaying mail directly to the SMTP Server.

Notes/Domino 6 and 7 Forum

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