Why are incoming faxes not accepted by the XPhone Server?

Incoming faxes are not accepted by the XPhone Server.  

Possible causes:

• The fax number is not assigned to any user in the XPhone Server 
• Under UM -> GATEWAY, the value entered in the "Maximum length of extension numbers" field is too small
• In the area UM -> FAX -> GENERAL, all (virtual) fax subscribers have been entered in the "PBX Routing" area. No valid fax number may be entered here
• No e-mail address has been entered for the user in the XPhone Server. This is only relevant if the fax document is delivered by e-mail, e.g. in Microsoft Office Outlook or IBM Lotus Notes 
• The PBX incorrectly indicates the receiver number (called ID), e.g. with country code without preceding + or one too few preceding zeros. Check the receiver number indicated in the voicemail log and if necessary correct the phone number indicated by the PBX in the PBX configuration