What's the 'from'-variable up to?

[Thorsten Haude]

Hi list,

I use
        set from="Thorsten Haude <[EMAIL PROTECTED]>
to change my address from local user to provider's user. It did not work
until I changed 'sendmail' from
        sendmail="/usr/sbin/sendmail -oem -oi"
to 
        sendmail="/usr/sbin/sendmail -oem -oi -f [EMAIL PROTECTED]"

So I ask myself, what's 'from' all about?

Thorsten