Sorting Mx servers using their preference number...

Once you've retrieved your mx lists, you want to be kind enough to gently contact mx server in their prefered order...

In erlang, sorting a list is done with sort function like 'keysort'.

SortedList = lists:keysort(1, List).

lists:keysort uses as first parameter, the nth element of the tuple to use in the sort, and as second parameter the tuple list you want to sort...

Once you've sorted your tuple list, you may want to remove the key you use to sort, lists:unzip remove this...

Finally, retrieving a mx list, sorting it, and directly using it can be done like this:

mxlist(Domain) ->
 List = get_mx(Domain),
 {_, Hosts} = lists:unzip( lists:keysort(1, List) ),
 Hosts.