Question : what msstd in outlook anywhere used for?

i have setup outlook anywhere RPC over HTTPS  on my exchange. I tried to enter msstd:FQDN and also tried not to enter it. Both of ways work. So what is that used for?
see the iamge for example

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test-rpc-over-http-8-.gif (11 KB) (File Type Details) 

msstd

Answer : what msstd in outlook anywhere used for?

MSSTD stands for Microsoft Standard form, don't know why it works both ways but I've also noticed that, although I had some instances where outlook did not work without the prefix.

as a side note I had trouble remembering this stupid prefix so now I remember it as :

MicroSoft Sexually Transmitted Disease :)