If you need groupOfNames to show addresses (i.e. for a distribution list), you 
can use the proxyAddresses which I found on the Microsoft website.  I import the
following schema in slapd.conf and use the following form for proxyAddresses:
        SMTP:First Last <user@example.com>
For my department lists, I put the manager in as the email address and then add 
everyone else as proxyAddresses so that the manager's address shows up in the 
Outlook Address Book without opening the entry. The MS website says 
proxyAddresses is limited from 1 to 1123 entries, so it may not work in all 
situations.  I'm using the back-sql module with the patch to fix the unixODBC 
crashing with mysql, and although it's slow, it does work.  I return multiple 
records instead of one big line of text, I'm not sure how an LDIF would be 
formatted but I'm guessing just like multiple emails. I merged the nisMailMembers
formatting with the proxyAddresses ID to get the following schema, though something
else might be better since I'm no expert. Anyway, I couldn't find anything on
the web regarding success in getting Outlook to group multiple emails with a 
distribution list (except by sticking on big line in the email string), so I 
thought here would be a good place to post the info.  I've only tested this 
with Outlook XP/2002, but I would think it would work with other versions as well.

attributetype ( 1.2.840.113556.1.2.210
        NAME 'proxyAddresses'
        DESC 'rfc822 mail address of group member(s)'
        EQUALITY caseIgnoreIA5Match
        SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )