applies to version 5.1.2

similar bugs for mail() on Windows, but software-related, are 28038, 37073. Mine is documentation-related.

AFAICT "Return-Path" isn't set by PHP at all unless you specificly put it in the headers yourself.

The sendmail_from however seems to override (if specified) the "From" header which either needs to be documented or fixed.

Possible fix: http://php.is/bugs/37122/win32.sendmail.patch.txt

(Reclassified as php bug).
-Hannes

The comment from bjori@php.net does not match what I have observed, in Windows. I observe exactly the opposite, sentence by sentence.

I looked at the mails produced on the receiver side, of course. Others have also observed, and reported, that sendmail_from makes the Return-Path: header.

I've managed to get my hands on windows machine to verify this.

It is correct, for what ever reason the sendmail_from php.ini directive is used as "Return-Path" too and it can't be changed via the additional_headers parameter.

If "From:" header isn't set as additional header the sendmail_from ini directive is used.

How do you feel about the following patch?
http://php.is/bugs/37122/win32.mail.ini.patch.txt

First big thanks that you did something on my report. 

I'm not fluent in the php-manual editing or in english language, but it works yet a bit different:

"sendmail_from": Which "Return-Path:" mail address should be used in mail sent from PHP under Windows. (If not set, and From: is given in $headers, From: gets duplicated as "Return-Path:" as well. If none is set, mail() does fail. Again, this is for Windows).

Please note at least three points: 
- I don't know why Return-Path: seems required by SMTPs, but every single mail I looked at has it. According to RFC2822, Sender: would be more required, but it never occurred to me.
- mail() on Windows is entirely different from mail() on Un*x. 
- mail() is mainly for beginners like me. Experienced people (like I'll be, soon) use PHPmailer, and later go for PEAR::mail.

Nevertheless it makes sense to have mail().

> "sendmail_from": Which "Return-Path:" mail address should be used in mail sent from PHP under Windows.
> If not set, and From: is given in $headers, From: gets duplicated as "Return-Path:" as well.
It's not a PHP "problem", it's your MTA that does this. But I do think we should apply my previous patch.

> If none is set, mail() does fail.
It is noted at php.net/function.mail that the "From:" header is required.

> Please note at least three points:
Your last two are noted in the manual

-Hannes

This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation better.

"This directive also sets the "Return-Path:" header."

May I suggest:
"sendmail_from: what to use as FROM in the SMTP Transaction. (If missing, From: from the headers is used as FROM)"

Comment to this: In fact the header fields From: and Return-Path: are not really relevant, but FROM is relevant. I wasn't aware of the difference between SMTP commands and mail headers when I initiated the bug.

Sure, you may suggest it :), but I think it will only confuse people even more.

-Hannes