The specified error means that an SSH scan attempt was made for the Mitel phone, but do keep in mind that SSH scanning is mostly designed to scan Linux, Unix, and Mac computers. In general, network devices should be scanned using a different protocol, preferably SNMP. The SNMP protocol will give back the most information for your network devices.
We would recommend that you go through the following steps:
Consult your device documentation for information on how to enable SNMP.