When I try and install SEP 12.1.4 on OS X 10.6.8 I get "Incompatible version of Mac OS X.  This software requires Mac OS X 10.7 or higher"

So what's the most recent version compatible with 10.6.8 please?

SEPM 12.1.3 are compatible Mac OS X 10.6.8, 10.7 (32-bit, 64-bit); 10.8 (64-bit).

System Requirements for Symantec Endpoint Protection, Enterprise and Small Business Editions, and Network Access Control 12.1.2 and 12.1.3

See here:

System Requirements for Symantec Endpoint Protection, Enterprise and Small Business Editions, and Network Access Control 12.1.4

Mac OS X 10.7, 10.8, 10.9

For 12.1.4.1 and higher:

System Requirements for Symantec Endpoint Protection, Enterprise and Small Business Editions, and Network Access Control 12.1.4.1/12.1.4.1a

Mac OS X 10.7, 10.8, 10.9

You will need SEP for Mac 12.1 RU2 (12.1.2015); that is the most up to date version of SEP for Mac that works with OS X 10.6.8. There never was a SEP for Mac 12.1 RU3 client.

There is a SEP for Mac "legacy" package that can be imported into an RU4 SEPM.

SEPM>Admin>Install Packages>Client Install Packages>Tasks>Add a client install package...

Browse into the folder containing the SEPM install files>AdditionalPackages folder. Choose SEPMacLegacy.info; it imports a SEP for Mac 11.0.7 package that works with both PPC and Intel.

Hope this helps!

MJD

Many thanks for these excellent replies, I am hoping to get a chance to deal with this today.