DHCP options for MItel SIP phones on a Mivoice Office 400

When using an external DHCP server. Procedure is very simple:

Define vendor class.
Set predefined options (String, Code=02)
Set scope options: 1.2.3.4 (Substitute 1.2.3.4 with the PBX IP).
No specifying of HTTPS / FTP / TFTP needed

The above will setup Option 66 on a Microsoft server.