> We have a cluster of Itanium blades running OVMS  V8.3-1H1 [...]

   As usual, showing actual commands with their actual output can be
more helpful than vague descriptions or interpretations.  For example:

      tcpip show version

> However, on another 2-node cluster within the same LAN, e are able to
> send mail to the same user without creating an MX record.

   So, why, exactly, are you playing around with creating MX records
which you apparently do not need?

> [...] and using DNS.

   As I read the TCPIP HELP, SET MX_RECORD "[...] adds routing
information to the local Mail Exchanger (MX) database."  If you're using
DNS, then why, exactly, are you playing around with creating MX records
in the local data base which you apparently do not need?

> After running the SMTP configuration, [...]

   And that tells me what, exactly, about the SMTP configuration of this
system?  And how is it different from the other system, where everything
works?

> [...] we tried to send mail to QAUser1@qasmtp.sgx.com [...]

   Why "@qasmtp.sgx.com" instead of "@sgx.com"?  What, exactly, is
qasmtp.sgx.com?


> %TCPIP-E-MXERROR, error processing MX request
> -RMS-F-RAC, invalid record access mode

   I know nothing, but I'd guess that someone has damaged the routes
data base file (possibly by attacking it with a text editor).  Around
here:

ALP $ pipe dire /full TCPIP$ROUTE | search sys$input organization
File organization:  Indexed, Prolog: 3, Using 2 keys

If you see something else, then you might want to resore a valid file
from a backup, or perhaps delete the damaged file, and create a fresh
one:

      tcpip help create route


   "Why TCPIP$ROUTE?", I hear you cry.

ALP $ tcpip help set mx_record
[...]
       The local MX information is stored in the routes database.
[...]