If you want to configure the port of the back-end HTTP Messaging Server with the Messenger Express Multiplexor, use the following configutil command on your Multiplexor machine:
local.service.http.proxy.port.hostname
where hostname is the host of the back-end HTTP Messaging Server.
For example, if the host name of the back-end messaging server is sesta.com and the port number is 8888, the command would be in the following format:
configutil -o local.service.http.proxy.port.store.sesta.com -v 8888
local.service.HTTP.proxy.port applies to all back-end message stores except those which have their own port (same as local.service.proxy.admin).