What steps should a systems administrator take to prevent his or her company's
e-mail from being filtered as spam/UCE/bulk-mail.  I want a general
list of pitfalls to avoid that will increase the likelyhood that your
e-mail will be filtered into a spam folder by Yahoo, Google, Hotmail
and the like.  Included in that list, I want to know if there is an
increased danger in this scenario: the domain name of the server
sending the e-mail is different than the e-mail of the "from" address.
 Example: the header says, "Recieved: From company_A.com" and also
says "From: user.name@company_B.com".

There is definitely an increased risk of your email being treated as
spam if you are using a from domain address that does not match the
domain registration's IP range.  As far as I know, SenderID / Sender
Policy Framework is in the process of being adopted by GMail, Hotmail,
and AOL ... don't know what Yahoo is actually doing in this area.  SPF
is a superset of SenderID and basically uses DNS data for the From
domain to validate if a particular IP is authorized to send mail from
it ... details here http://www.openspf.org/faq.html

Some senders have said in the recent past that they plan to block
non-SPF validated email, but at the very least it is being used in
spam scoring (determining the probability that an email is spam), as
Gmail, hotmail, and AOL all have spf validation headers in received
mail.

Another thing you can do to protect yourself is to pay to be bonded as
a non-spammer ... I think this is a little expensive, and there are
some liabilities you assume if you undertake this, so have your legal
team look into this before signing up (http://www.bondedsender.com/). 
Finally, you can monitor spam blacklists, there are a few tools out
there to do this, but off hand I can't remember the name of the one
I've used.

Hope this helps,
Kindageeky

By the way, there are some hoops you can jump through to SPF
validation even if you have FROM addresses foreign from your own.  As
I don't want to help spammers out there by posting this technique
publicly, shoot me a gmail at my username less the "-ga" if you'd like
details.

Thanks kindageeky.  That is good information.  Also, just FYI, I
posted this question because I coudln't find a good search phrase for
this topic.  I have now found that searching for the words "avoiding
spam filter" is a good way to start.