SMTP Response: 554 5.7.1

[coper]

Hello again,

I'm having a strange problem. I can use email accounts without a problem except from a particular office. Inside that office I can use webmail but when I try to send emails using an email software I get this error:

Code:

"The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'mail@domain.com'. Subject '', Account: 'mail.mydomain.com', Server: 'mail.mydomain.com', Protocol: SMTP, Server Response: '554 5.7.1 <mail@domain.com>: Relay access denied', Port: 25, Secure(SSL): No,
*Server Error: 554, Error Number: 0x800CCC79

And I get this in the server logs:

Code:

Jul 27 17:32:33 webserver1 postfix/smtpd[14643]: warning: 190.210.26.245: address not listed for hostname customer-static-210-26-245.iplannetworks.net
Jul 27 17:32:33 webserver1 postfix/smtpd[14643]: connect from unknown[190.210.26.245]
Jul 27 17:32:33 webserver1 postfix/smtpd[14643]: NOQUEUE: reject: RCPT from unknown[190.210.26.245]: 554 5.7.1 <mail@otherdomain.com>: Relay access denied; from=<mail@domain.com> to=<mail@otherdomain.com> proto=SMTP helo=<ladc>
Jul 27 16:32:55 webserver1 postfix/smtpd[3617]: disconnect from unknown[190.210.26.245]

Could anyone help me with this?

Thanks.

c.