SquirrelMail v1.4.21 failed to send mail from specific PC
Having a pretty weird problem. We have squirrelmail running on our server. One of our client having problem sending mail through squirrelmail couple of hours ago. But he can send email from email clients (outlook). Other users also not having problem. We tried to send email using his account from different PC's using different browsers. From some PC it's working from some it's not. The error message is "550 5.1.0 <.net@DOMAIN-NAME.net>: Sender address rejected: User unknown in virtual mailbox table;". Postfix log showing " NOQUEUE: reject: RCPT from mail. DOMAIN.com[127.0.0.1]: 550 5.1.0 <.net@DOMAIN-NAME.net>: Sender address rejected: User unknown in virtual mailbox table; from=<.net@DOMAIN-NAME.net> to=<email@example.com> proto=ESMTP helo=<webmail.DOMAIN.com>
Any idea? Thanks.