> When I use mail() function not every email server accept this
> emails. But everything is ok if sending from the same mail server
> using outlook express.


Mail servers might not let you send mail through them for a variety of
reasons.  Usually, these rules are set up to prevent spammers from using their
bandwidth and process power to send junk mail through them.

Some rules might be that the client sending the mail via SMTP must be on a
particular subnet or network.  The "from" address of the email might need to
belong to an accepted domain name, the MAC address of the sending machine
might need to be registered, etc...

The list goes on and on.

I'd ask the sysadmin of the SMTP server about what restrictions are in place,
and if what you're trying to do is allowable.


nik