Arne's questions

My exim4 server rejects a lot of spam emails due to failed sender verification. However, those result in lots of frozen messages, which in turn spam my postmaster inbox. Example line from exim log:

2020-08-13 15:39:28 [25544] H=(mail.foo,com) [::1]:14347 I=[::1]:25 F=<[email protected]> rejected RCPT <foobar@localhost>: Sender verify failed

And then I will get a notification like this in my postmaster account:

Message 1k69l3-0007T7-Hv has been frozen (delivery error message).
The sender is <>.


The following address(es) have yet to be delivered:
[email protected]: Unrouteable address

I guess my exim4 wanted to send a bounce message, which in turn can't be delivered. How can I avoid this?

I am running exim4 on a vanilla Debian Stable system. The machine has proper DNS A and MX records. I want to use it as a mail server.

SMTP with TLS already works fine for authenticated users.

However I can still telnet from somewhere else to the server using smtp and send mails to my own domain by spoofing the MAIL FROM and picking the right RCPT TO.

How can I configure exim so that only real mail hosts with MX record can use unauthenticated SMTP?

We have a CUPS based color laser printer. Our colleagues often tweak their print settings, resulting in non optimal configurations. E.g. they change the color reproduction so that even black and white text will be printed in full CMYK. This can be avoided by setting the "Color reproduction" CUPS printer setting. However, right now this can be overriden by the user. Is there a possibility to force this setting on the CUPS server?

The documentation of vsftpd is quite good (https://security.appspot.com/vsftpd/vsftpd_conf.html), however I cannot find some details on how to use public key authentication. I know that I need require_cert and maybe validate_cert, but where do I put the public client keys, which are accepted for authentication? I cannot find information on that.

I upgraded our site to Typo3 4.5. The workspace extension has changed significantly. We have a very flat organizational structure, without separate editors, reviewers and publishers. Our editors should edit in the Draft workspace, and then be able to directly publish. They can do this right now, by clicking the checkboxes in the Workspace module, and selecting "Publish to LIVE". However, when they mistakenly click "send to next stage", they will not be able to publish it themselves anymore. Only admin will be able to do that in our configuration. Can I disable this stage stuff, because we do not need it at all?