EUDC lets you maintain a list of frequently used servers so that you
can easily switch from one to another. This hotlist appears in the
‘Server’ submenu. You select a server in this list by clicking on
its name. You can add the current server to the list with the command
M-x eudc-bookmark-current-server. The list is contained in the variable
eudc-server-hotlist which is stored in and retrieved from the file
eudc-options-file. EUDC also provides a facility to
edit the hotlist interactively (see The Hotlist Edit Buffer).
The hotlist is also used to make queries on multiple servers successively (see Multi-server Queries). The order in which the servers are tried is the order they appear in the hotlist, therefore it is important to sort the hotlist appropriately.
The name of a file where EUDC stores its internal variables (the hotlist and the current server). EUDC will try to load that file upon initialization so, if you choose a file name different from the defaults ~/.emacs.d/eudc-options, be sure to set this variable to the appropriate value before EUDC is itself loaded.