Doublebounce sets `From:` to `<#@[]>` which is rejected from remote

[Commifreak]

Hi.

Nullmailer v. 1:2.1-5.

I configured doublebounceto. However, I got a mail to send. That mail came back, because ... User unknown. So far so good, so nullmailer tries to send back to the original sender. But that was non exitent mailbox. At this point:

From: Message Delivery Subsystem <MAILER-DAEMON@me>
To: <originalsender>

Now, nullmailer uses my doublebounce BUT it sets Headers as follows:

From: Message Delivery Subsystem <MAILER-DAEMON@me>
To: <>

correct - To is empty.

The log for this try:

May  4 18:02:44 qlb-wwwint-1804 nullmailer-send[1138]: Starting delivery: host: server protocol: smtp file: 1651680164.8025
May  4 18:02:44 qlb-wwwint-1804 nullmailer-send[1138]: From: <#@[]> to: <doublebounce>
May  4 18:02:44 qlb-wwwint-1804 nullmailer-send[1138]: Message-Id: <1651680164.017703.8026.nullmailer@qlb-wwwint-1804>
May  4 18:02:49 qlb-wwwint-1804 nullmailer-send[1138]: smtp: Failed: 553 5.1.8 <doublebounce>... Domain of sender address #@[] does not exist
May  4 18:02:49 qlb-wwwint-1804 nullmailer-send[1138]: Sending failed: Permanent error in sending the message

It seems, that doublebounceto is not set as To? And now the remot rejects due to ... Domain of sender address #@[] does not exist.