After upgrading to iRedMail 0.5.0 I configured disclaimer. It seems that amavisd correctly put the testing disclaimer to every outgoing mail. But it is not showed by the receiver mail client.
The disclaimer is actually present in the message:
Content-Type: multipart/alternative; boundary="=_d8a63e2b9b1019e220f3664d76a57869" --=_d8a63e2b9b1019e220f3664d76a57869 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="UTF-8" This is a test! [b]Testing disclaimer.[/b] --=_d8a63e2b9b1019e220f3664d76a57869 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="UTF-8" <p>This is a test!</p> --=_d8a63e2b9b1019e220f3664d76a57869--
Disclaimer won't appear into text/html version of messages! And even if I select "Plain text" into Roundcube, it seems to send messages with HTML code...