send mail as other user (alias)

[hede]

Am Wed, 23 Apr 2014 14:29:38 +0200
schrieb Jelle Langbroek <jelle at orkz.net>:

> Hi, thanks for your reply. I understand.
> Is there a way to protect this behaviour on my kolab server? I want
> people not to be able to impersonate others.

Actually this should be the default. 

In main.cf there should be:
submission_sender_restrictions = [...] check_policy_service unix:private/submission_policy [...]

And in master.cf there should be submission_policy using /usr/lib/postfix/kolab_smtp_access_policy to verify the sender.

All using the submission port (587).

Sending via port 25 (smtp) should be disabled at all. -> "554: Relay access denied" even for successfully logged in users.

regards 
hede