I don't know of any resource that spells them all out. I can tell you a couple ...
Waitforauth - if 1, new players are placed in the introduction area (newgate.are). They then need to have immortal approval before they can leave that area (for the name they have chosen). Otherwise they start in New Darkhaven.
Nameresolving - if 1, name resolving of players is disabled (ie. it remembers an IP address, not a name)
IdentTries - number of times it tries to connect to an "ident" server to look up a connection. Set to zero to disable.
MudName - name of your MUD (put a ~ at the end).
eg. MudName Nick Gammon's MUD~
As for the rest, you would have to work them out from the source. Most of them will be levels at which you can do something. I will work through one as an example. I am using Cygwin shell here to search for things, but any editor with a "find in files" capability would do the same thing. What I type is in bold.
Let's look at this line:
Writemailfree 51
Straight away I would guess that you need to be level 51 to write mail "for free" - whatever that means, just from the name. However, let's explore in more detail ...
Let's search for that exact word in the source ...
$ grep Writemailfree *.c
db.c: fprintf( fp, "Writemailfree %d\n", sys.write_mail_free );
db.c: KEY( "Writemailfree", sys->write_mail_free, fread_number( fp ) );
OK, that tells us that the word "Writemailfree" in the sysdata.dat file is put into the variable "sys.write_mail_free".
Now let's search for what that does ...
$ grep write_mail_free *.c
... some lines appear here ...
boards.c: if (get_trust(ch) < sysdata.write_mail_free )
... some lines appear here ...
Amongst the various lines that appear, the above one looks relevant because it is testing the value of write_mail_free.
So, let's edit boards.c and see what the test is all about ...
if (get_trust (ch) < sysdata.write_mail_free)
{
quill = find_quill( ch );
if (!quill)
{
send_to_char("You need a quill to write a note.\n\r", ch);
return;
}
if ( quill->value[0] < 1 )
{
send_to_char("Your quill is dry.\n\r", ch);
return;
}
}
Right, there is the answer. You need to be level 51 to write mail "for free", and if you are below level 51, then you need a quill to write mail (notes).
If anyone knows straight away what the others do, that would be great to hear from them. Otherwise, if you work out what they do, please post your results here, so others can benefit from your knowledge.
Also, read doc/SMAUGDOC file that came with SMAUG, that has a lot of helpful information in it.