-f option in mail() and sender (2 questions)

[Floezen]

I have two question concening sending mails thru php

1.)
What does the -f option (envelope sender address) exactly mean? And how would I set this option in this case:
From: My Name <mail@domain.tdl>

Here an example:

to_address@domain.de, Test Mail, Dies ist eine Testmail, Message-ID: <20001239639825.359anything@sender.de>
From: My Name <mail@sender.de>

Where would I set the -f?

2.)
When I have a mail as in the example above, the mail queue shows something like
anonymous@sender as sender. Only if I add a Return-Path I get the Return-Path address shown as sender.
- Is this correct?
- Why isn't the From address used as sender?
- Can this make difficulties sending emails (i.e. mailservers not accepting these mails)?

Thanks
Flözen

[Jake Arkinstall]

The -f is the from address:

mail(..., ..., ..., '-fmyemail@domain.com'); 

IIRC that shows up as the sender.

[Floezen]

So

mail($email, $subject, $message, '-fmail@domain.de'); 

and

mail($email, $subject, $message, 'From: mail@domain.de'); 

are the same?