> Our ISP says we are running Solaris version 2.6.
 > LISTSERV SHOW VERSION says "Running under: SunOS 5.6"

Solaris is SunOS 5.x plus supporting cast.  Or something like that.
Your ISP is running Solaris 2.6, which is based on SunSO 5.6.
The version stamping and terminology perpetrated by Sun is deplorably
confusing.

In popular terminology, SunOS refers to SunOS 4.x or older, and
Solaris refers to the newer stuff.

 > So which Unix platform version do I choose for updating LISTSERV classic
 > (SunOs?)?  Here are the choices:
 >  > ===========================================================
 >  > Solaris.tar.Z

This is for Solaris running on Sparc hardware.

 >  > Solaris86.tar.Z

This is for Solaris running on Intel hardware.

 >  > Solaris-OCI.tar.Z

This is for Solaris running on Sparc hardware, but includes the
interface to Oracle databases, for doing mailmerge and similar
nifty stuff.

 >  > SunOS.tar.Z

This is for SunOS 4.x.

Dennis Boone
H-Net