email was sent "on behalf of"

[necron]

This is a weird problem and I can't figure out what caused it, nor can I find any documentation on it:

I send an email using PHP and the email ended up arriving at the recipient with following FROM header:

-----Original Message-----
From: [e-mail] [mailto:[e-mail]]On Behalf Of [e-mail]

The strange thing is that I set the From and the Reply To headers of the email to be [e-mail]. The [e-mail] is the default email address in the php.ini.

What does "On behalf of" mean?? Why is it being sent on behalf of? The problem this causes is that if the recipient of the email tries to reply to the email, his reply will go to [e-mail], not to [e-mail].

Does anybody know how to fix this? Thanks heaps!

[TheDefender]

Well, we could write you some code, but it won't do you any good... Try posting your code, and we can provide a little better help.