Miwojedk You might be missing my point. I'm saying with the variables I can use, that's not possible without re-naming the server.
That's the way the private messages are formatted so hopefully you can see the options I have to play with, I can't statically set that to [F1] without it breaking other functionality elsewhere, as I have no way to change that without it changing the server name everywhere, and quite frankly I don't want to do that...
It surprised me but it happens a fair bit when people are in the hubs sending messages and when we had SMP running that would happen a fair bit where someone would move to the SMP server and the other player wouldn't.
Currently the only way to change it is to change the format as you can see there (And it probably makes sense for the receiver not to see their server and the sender not to see their server given they should know what server they're on...).
The options are to customise that message within reason, though I personally think the person who is not "You" should always display what server they are on in the message, or we disable the cross-network messaging entirely which I'd rather not do, but is an option.