E-Mails sent by ISPConfig itself and envelope from address
Since ISPConfig is not using a modified sendmail_path with custom -f parameter which defines envelope from address, emails are being sent with envelope address "ispconfig@serverhostname". For example, billing emails (billing module), quota warning notifications, etc. Even when "From" address is configured in the billing module or even in Main ISPConfig configuration. Yes, header From is set up correctly, but envelope from is not configured by From header.
The reason why I am opening this issue is that due to lack of proper envelope from address the stuff cannot properly deal with undelivered emails - eg. billing email or even quota notification emails. Sure, the solution may be configure redirect from "ispconfig@serverhostname" to another address (not to mention about the ugliness of the address) or put into fastcgi wrapper sendmail_path as well as for any other website with a parameter -f but there will be an only static address. I would prefer to much variable approach which will accept "From" address configured in ispconfig interface (either for billing or system-wide in main config). We are using custom sendmail wrapper when envelope from is configured by From address but from some reason, it malform emails sent from ispconfig (due to multipart sections). I did not investigate it (maybe it is a problem with our wrapper but on all servers and different websites it works properly). Until then (its ours thing) I did a quick change in the ispcmail class with added extra param into mail() function where I changed:
$result = mail($to, $enc_subject, $this->body, implode($this->_crlf, $headers));
$result = mail($to, $enc_subject, $this->body, implode($this->_crlf, $headers), "-f $this->_mail_sender");
So, if you guys consider this as useful for ispconfig and the right approach, this can be used in the ispconfig release.