I am using Exim and Dovecot. I want add to all outgoing email an anti-abuse header like:

X-Report-Abuse: TEXT to report abuse

How I can do this? Thanks in advance

Thanks, this is not helping me. I added the line where you told but also incoming email have the X-Report-Abuse heder.

I cannot find that on my Exim

send_to_gateway:

I added the headers_add = X-Report-Abuse: TEXT to report abuse here:

This transport is used for delivering messages over SMTP connections.

remote_smtp:
      driver = smtp 
      dkim_domain = ${lc:${domain:$h_from:}} 
      dkim_selector = x 
      dkim_private_key = /etc/exim/dkim.private.key 
      dkim_canon = relaxed
      headers_add = X-Report-Abuse: Please report any abuse text

this is working if the outgoing email are sent from an email client, is not working if email is sent by SMTP from a PHP script or app like wordpress or other PHP app.

This adds a header to outgoing messages:

Add this line to your exim.conf file within your outgoing router(s) configuration:

headers_add = X-Report-Abuse: TEXT to report abuse

For example

begin routers

...

send_to_gateway:
  driver = manualroute
  domains = !+local_domains
  transport = remote_smtp
  route_list = * smtp.myisp.net
  headers_add = X-Report-Abuse: TEXT to report abuse

dnslookup:
  driver = dnslookup
  domains = ! +local_domains
  transport = remote_smtp
  ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
  headers_add = X-Report-Abuse: TEXT to report abuse
  no_more