php sendmail addresses = @server1.example.com

[aldo]

All emails sent by php from a website (Debian 6 / ISPConfig3) have the same address (web20@server1.example.com).

The smtp server of the recipient sees as the sender:
web20@server1.example.com

MAIL FROM: <web20@server1.example.com>

Trying to use a relayhost in the log of the same I see:

MAIL FROM:<> AUTH=<>	250 Requested mail action okay, completed	43	22	sm	
MAIL FROM:<> AUTH=<>	250 Requested mail action okay, completed	43	22	sm	
RCPT	RCPT TO:<web20@server1.example.com>	250 Requested mail action okay, completed	43	37	sm	
RCPT	RCPT TO:<web20@server1.example.com> 250 Requested mail action okay, completed	43	37	sm

In the above example, the message was sent to two recipients, each of which has been replaced.

Thank for any help.

[aldo]

I changed the domain name changing /etc/mailname but I would like to use the site domain name instead of server domain name.

Is that possible?

Thanks.