[exim] Header question, X-Relay-User

Hi there,

above all, thanks for being able to join this board!

Well, I have an account on a ubuntu webserver, running exim4 as sendmail
replacement. And,

I want to prevent exim from sending out the "X-Relay-User" header line.

Reason behind is, that I am running a real email account together with
several email redirects to this single email account. So, whenever such a
redirect / forwarding address is being spammed, I can simply close it and
open a slightly different one and use this instead.

This only works securely as long as the name of the "real" email account
is not written into the "X-Relay-User" line when sending from this
account.

The funny thing is:

When accessing /usr/sbin/exim4 locally, then Squirrel email client is
able to write the header without "X-Relay-User" info. But,
when accessing exim via smtp on a different box then this directive is
ignored and the real email address is part of the header.

Does exim only accept customized headers when called from /usr/sbin/exim4?

Is it part of the default settings to write this info into the header?

Can exim be told to not write X-Relay-User even when called via smtp?

Thanks for any info!

Best regards,

Markus