You must look in Local Network :
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Add or remove local networks
For security reasons, several services on your Mitel Networks server are available only to your local network. However you can grant these local access privileges to additional networks by listing them below. Most installations should leave this list empty.
Click here to add a local network.
Additional networks with local access privileges
Network Subnet mask Number of hosts Router
xxx.xx.xx.xx 255.255.255.255 1 default Remove...
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This way you permit access to XXX.XX.XX.XX to your machine and can specify with mask a range of IPs.
I used it to permit access to mail server from a remote location and it works fine for me. Another IP can“t access to mail server.