I was setting my my mail server and looked at the e-maill address and decided that I didn't like it, It ends in the @localhost.localdomain. This is was is in my host name and I was wondering if I can change that host name or not?

care to expand on what you're actually doing? where are you seeing this address? what server packages are you using?

What I am trying to do is set up Evolution of my computer. When I go through the set up wizard at the begin, It has two fields that are already filled out, one is my name and the other is the e-mail address. The one that is given is my usernam@localhost.localdomain and when I looked at my host name in my Internet connections, that is the given user name. Is there a way that I can change this to something different or am i stuck with this as a host name?

I think you're meaning:
/etc/hostname
and
/etc/domainname
You can do, as root:
Newname > /etc/hostname
Newname > /etc/domainname,
and that should change you're host/domainname.
Don't know if this is what you're meaning, but trying this can't do to much harm, especially not after:
cat /etc/hostname > /etc/hostname.old
cat /etc/domainname > /etc/domainname.old,
and then doing the above, so you've got a backup.

Gave that a shot, now when I log on. I don't have a hostname any more
Don't know what I did, but I lost it.

When I start my computer up, I see a mesage that the dhcp fails to start up. how do I fic that problem, plus whwn I exit my kde, I see a message that say Unable to get hostname, your system is misconfigured. I've found some files that have my original host name in them, but I can't seel to get the computer to see them

Any ideas?

I'm sorry if I messed things up for you in first place, didn't meen to.

But, I hope you made a backup like I said, so you should set back the backup, like:
$ cd /etc
$ mv hostname.old hostname
$ mv domainname.old domainname.

Now, I gave you some wrong advice maybe, their exists a command to change your hostname.

If I want to change my hostname to foo, logged in as root, I type:

# hostname -v foo
which gives as output:
Setting hostname to `foo'

Then it works, and after you simply issue:

#hostname
with no arguments, it says:
foo
.
domainname works the same, issuing dommainname in the command line with no arguments yields your current domainname, and saying domainname followed by a name sets your domainname to that name.