OpenVMS contains two logical names to enable you to customize
the operation of certain Mail functions on your system. This includes
checking the network address format to use and sending mail directly
to a user on an OpenVMS Cluster (rather than through the network)
if the sender and recipient are both on the same node.
You customize Mail by defining the logical name MAIL$SYSTEM_FLAGS as a system
and executive mode logical name. For example:
$DEFINE/SYSTEM/EXECUTIVE_MODE MAIL$SYSTEM_FLAGS 1
The value of the logical name MAIL$SYSTEM_FLAGS is interpreted
in the following ways:
Value
Meaning
1
Indicates that this node
is part of a homogeneous OpenVMS Cluster system. In other words,
all disks are accessible to the cluster, and a common SYSUAF file
and a common mail file exist for the cluster.
When this
bit is set, the system checks the node to which you are sending
mail to see if it is currently in the cluster. If the node is in
the cluster, the system bypasses DECnet, and the message is written
directly to the recipient's mail file. (Note that the node must
be up to determine whether it is part of the cluster.)
2
Directs Mail to set the
OpenVMS Cluster system breakthrough flag when issuing the $BRKTHRU
service to notify the recipient of new mail. This flag is used only
in OpenVMS Cluster systems and, typically, only in homogeneous OpenVMS
Cluster systems (in other words, flag 1 is also set).
4
Directs Mail to include
the time the message was delivered in the notification message displayed on
the recipient's terminal.
Directs Mail to use DECnet
VAX address syntax when the system is running DECnet-Plus.
16
Directs Mail to use DECnet-Plus address
syntax.
32
Indefinitely retry reading a UAF record
when the record is locked by another user. Default (bit not set)
behavior is to return UAFGETERR and not retry.
For example, if MAIL$SYSTEM_FLAGS translates to 7, the system
selects the first three flags. If the logical name does not translate,
the default is 0, which indicates that no flags are set.
On VAX systems, if neither 8 nor 16 is in the value for MAIL$SYSTEM_FLAGS,
the system checks to see whether DECnet for OpenVMS or DECnet-Plus
is running on the system and operates as if the appropriate bit
were set. If MAIL$SYSTEM_FLAGS accidently specifies both DECnet
and DECnet-Plus, the Mail utility defaults to DECnet-Plus.
Certain network addresses can be interpreted by the Mail utility
as either DECnet-Plus names or SMTP names. These ambiguous network
names have the following features:
The address does not contain double
quotation marks (")
The address contains an at sign (@)
There are no periods to the right of the at sign
You can control the default system interpretation of those
names with the MAIL$INTERNET_MODE logical name.
To specify the mail address mode, define logical name MAIL$INTERNET_MODE
as follows:
$ DEFINE/SYSTEM MAIL$INTERNET_MODE address_mode
You must have SYSNAM privilege or write (W) access to the
system logical name table. The following table describes the values
of address_mode and the effect of each value of MAIL$INTERNET_MODE.
Address Mode
Effect
HYBRID (default)
If the node component of
the address contains a period (.), Mail uses SMTP address mode.
If there are no periods, Mail uses DECnet address mode.
DECNET
Mail always interprets the
node component of the address as a DECnet node specification.
SMTP
Mail always interprets the node component
of the address as an Internet address specification. The default
address mode is SMTP unless you use logical name MAIL$INTERNET_TRANSPORT
to define a different transport (and therefore different address
mode).
For more information about using logical names to control
the use of internet address modes by the Mail utility, see the OpenVMS
User's Manual
.
HP OpenVMS System Manager's Manual, Volume 1:... 
Customizing the Operating System
