How big is a VAX 8600 running Ultrix?

[lerner at isi-vaxa.arpa]

In answer to your question Karl ...   yes.  But, I'm not shure what 
you really mean by "smart terminals" that decrease cpu load and, it depends
upon what kind of mailer software you run and how the terminals interface
to the system, ect.

Have you looked into a Sun3 configureation?  It might be less expensive, both 
at the outset and in maintainance cost (I am be subtle here by just mentioning 
maintainance instead of downtime and hardware trouble).  

We have an 8600 running 4.3bsd and It's got at least 100 users on it (probably
not all running at the same time yet) and It doesnt seem daunted at all.  

I dont know how many sun3s it would take to handle your load (5, maybe less?)
and It might prove more fault tolerant (very subtle).  I've found SunUnix (based
on 4.2) to be better documented and more efficient than 4.2 or ULTRIX and it has
more support for networking applications (both sun's distribution and user development).

P.S.:
In that I dont know what you configuration really is, this may be entirley
off the wall but ... If you use terminal servers on the ether net and a SUN goes
down, then the user can just connect to another sun3 via the net, but if your
8600 goes down, then the whole show is cooked.

4.3bsd seems to a much better and faster implementation than ULTRIX or 4.2.