This is something that caught us out and judging by the posts to various forums appears to have caused others grief so I figured I’d document it here in the hope that other people find it and save themselves some hassle!
If you are running comms express on a frontend MEM/MMP machine with a backend mailstore service and you find that the tabs are sending you to the correct machine but port 0 (ie, blah.blah.com:0) then you need to set the variable
local.webmail.sso.uwcport on the backend machine(s). Restart the backend msging instance and the front end web/app server (the one hosting uwc) and the problem goes away.
Quite why this need setting on the backend is a bit of a mystery to me and it obviously confuses other people as well. Hopefully this will help someone out!
This is possibly only an issue with JES2 / 2005Q1 or greater – I think it was fine under 2004Q2 btw.