Assuming you are not in a Netware environment (I don't know if it will work the same).

MAKE A BACKUP OF THE MERCURY & MAIL FOLDERS. 

Copy the entire Mercury folder & mail folders to the SAME LOCATION on the new box (i.e. C:\Mercury -> C:\Mercury)

If you have to change location or drive letter you will need to edit the Mercury.ini and any .rul or other .ini files that have the old paths in them.

Start mercury on the new machine, ensure it runs as expected.

Stop mercury & run the latest installer, currently 4.52, 4.6 is due any day now [:)]  but don't wait for it because the 3.x series has some security flaws.

Make sure to choose the "Upgrade" option and it will pick up all your old settings.

Verify that it is working properly, THEN point your DNS to the new server and 'retire' the old one.

Shouldn't take more than about 30 mins. 

Hi there,

 For one of our customrs i have to emigrate mercury to another server.

Now i need to know what i have to keep in mind. And what is the easiest way to do that.

And big question i forgot , on the first system its the version 3.05, so i got to update before i copy the files and can there be any problems during the update

Thanks for ur help