Sending to FAX

[giancarlo64]

Hi,
in my mail server I have a Fax-modem where the received FAX will generate and email with a PDF attachment and to send an email I only have to send the email (with PDF attachemnt) to the receiver
FAX number followed by a @fax: Example 0444400033@fax
With email clients like thunderbird is no problem. If I try with roundcube it tell me that the email address is not correct and I can't send the email.
Where is the problem?

Regards

Gian Carlo

[alec]

Roundcube requires from domain part of email address to be a valid domain name or IP address. So, "fax" is not allowed here.