How to automatically implement a corporate signature for outgoing emails?

Question

postfix

Hello!
Here I ran into the problem of automatic ( html or txt ) signing of outgoing letters.
In the vastness of the Internet I found only one solution and it does not quite "work".
Given: Server raised with https://mailinabox.email/

Mail-in-a-Box is based on Postfix, Dovecot, Z-Push, Roundcube, ownCloud, Spamassassin, Postgrey, Nginx, @konklone's nginx config, and more.

$ postconf > https://gist.github.com/anonymous/58fa1db8afd4911de2d2

if you follow in the footsteps of what is indicated in the article on Habré, then nothing works,
apparently due to

/etc/postfix/main.cf: virtual_transport = lmtp:[127.0.0.1]:10025 #Spamassassin

and if I add content_filter=dfiltnot to master.cf but to main.cf, then postfix goes into loop 50, apparently because of the /etc/postfix/disclaimer: $SENDMAIL "[email protected]" <in.$$
question whether it is correct to add content_filter=dfiltto /etc/postfix/main.cf instead of /etc/postfix/master.cf

smtp      inet  n       -       -       -       -       smtpd
   -o content_filter=dfilt:

and already be smart about /etc/postfix/disclaimer so that postfix does not get into a loop.
Does anyone know another solution?