Hello Vicente,
as mentioned the Relay Server supported with SMP server runtime 3.0 higher then SP06 would be 16.5.x.
Please take a look at SAP Note 1904213 http://service.sap.com/sap/support/notes/1904213
(You can also access this Note via PAM http://service.sap.com/pam)
The RS architecture has changed completely(based on SQLA 17) so there is no compatibility with older versions.
If you are still running an older environment (SUP 2.2) you need to use the old version of RS.
If you want to upgrade your SUP 2.2 environment to SMP 3.0 MBO RUNTIME (which is similar to SMP 2.3) then you need to use the "old" Relay Server 16.x (Don't mix up with 16.5.x) which means at that point you could just do a simple upgrade of the existing RS 12 to RS 16.
A "quick" update process from RS 12 to RS 16.x you can find here:
http://wiki.scn.sap.com/wiki/display/SAPMOB/Relay+Server+upgrade+from+version+12.x+to+16.x+for+Afaria
Although this is for Afaria the process in general is the same, you just need to use the RS package from the SMP 3.0 MBO runtime server top update.
If you need a new RS 16.5.x you need to do a new installation from scratch accordingly to
http://scn.sap.com/docs/DOC-65929
Maybe you can elaborate more about your environment and if you want to upgrade your SUP 2.2 to 3.0 MBO runtime or to SMP 2.3.x?
Thanks and kind regards,
Andreas