Why is my fax not delivered to the recipient via Outlook?

If a user (or test user) sends a fax via the Outlook Client, it is not delivered to the recipient. In the log file "Mail2Fax" the error "Sender of mail message is unifiy messaging server itself" is generated.

The e-mail address of the fax sender corresponds to the e-mail address of the carrier for received fax and voicemail messages.

In the XPhone Connect Server, enter the e-mail address of the fax sender in the "Sender ID" section of the e-mail gateway in the administration interface. For "Sender ID" there must be an e-mail address that does not belong to any user. Save the setting and restart the selected UM services