[KLUG Members] RHCE exam info.

[Adam Tauno Williams]

>> I wouldn't consider someone an experienced or competent network
>> administrator unless they knew at least the basics of Sendmail.  
>> Like it or not you ARE going to encounter Sendmail 'in the field' 
>> and have to deal with it.  There are many things, particularly in
>> a directory enabled enviroment,  that Sendmail can do and others 
>> like Postfix cannot.  <aside>Also, sendmail isn't really any harder
>> to configure than Postfix - all you do with other MTAs is skip the 
>> step of turning your human readable configuration file into the 
>> actual configuation that is used.  They just do it themselves 
>> whereas with Sendmail you use M4 to do it.</aside>
> Many thanks for bringing that to my attentation. Could you tell me which
> directory features are not available in Postfix that you find in Send mail?

First, this isn't meant to denigrate Postfix at all.  Postfix is a very 
good MTA
and we use it on most of our servers,  they feed into the central servers that
run Sendmail (introducing a bit of controlled. heterogeniety is usually a good
thing anyway).

Postfix doesn't (or at least not that I have even been able to determine)
support 'configuration clusters'.  That is where these servers read this
configuration and those servers read that configuration and the configuration
is specified by name - this relates to objects in the Dit that are 
processed by
the servers.  And with sendmail *ALL* the classes can be stored in the 
Dit: access lists, relay lists, domains to be treated as local, generic 
rewriting
rules, virtual users, domain delivery method tables, etc...  This is primarily
because sendmail supports a generic concept of a "sequence" which is an
enumerable set of values,  and if an LDAP sequence type is implemented 
(it was,
fully as of 8.11.x) then that sequence can be used anywhere a sequence 
data type
is supports.  And in sendmail configuration sequences are used and supported
just about everywhere.  With an LDAP sequence a server can be told its 
'cluster
name' and then just uses objects from the Dit that are marked as beloning to
that cluster.  So our sendmail configurations are really just shells that fill
themselves from the Dit - we have two 'clusters' - morrisonFirewall for edge
SMTP servers and morrisonInternal for core SMTP servers.  Sendmail servers are
just set as one cluster or the other and a pretty much generic configuration
file is applied to all of them.

AFAIK postfix cannot match this level of LDAP integration.  Or else 
such featues
are just completely undocumented.  Maybe this will change,  but it 
appears to be
the situation now.  And there really isn't anything wrong, or terribly
complicated about, sendmail anyway.