PC Gen: How Global Groups Work When Sending Mail

• Microsoft Mail for PC Networks, versions 2.1x, 3.0, 3.0a, and 3.2

SUMMARY

Versions 2.1, 3.0, 3.0a, and 3.2 of Microsoft Mail for PC Networks have a very complex group structure. The global group definitions span many files. These files include:

   GROUP.GLB    (Contains the postoffice group names)
   GRPMEM.GLB   (Used for group folders.)
   ADMIN.GRP    (Contains tuple identifier (TID) values for group members)
   ADMINSHD.GRP (Shadow file of ADMIN.GRP)
   xxxxxxxx.MEM (Contains group member mailbags for external mail delivery)
   ADMIN.NME    (Postoffice address list)
   ADMINSHD.NME (Shadow file of ADMIN.NME)

The files that are accessed when mailing to a global group from the postoffice address list are:

   ADMIN.NME
   ADMIN.GRP
   GROUP.GLB and
   ACCESS2.GLB.

The GROUP.GLB appears to be an unnecessary component of the mailing process but if the GROUP.GLB file is missing or if the GROUP.GLB has been reset to a 4 byte header, then the user will receive a Notice 8," Error in transmitting mail or server disk is full." However, if the group's definition in the GROUP.GLB has a corrupted alias, address, TID (MEM filename), type, or delete flag, the group can still be mailed to from the postoffice address list.

The ADMIN.NME has a 45 byte record that contains the group's alias, TID (which for the group is the *.MEM filename), alias type (4 = group), and a pointer that is a byte offset into the ADMIN.GRP file where the group's definition begins. Each of the local user's addresses are also stored in the ADMIN.NME.

The ADMIN.GRP is a linked list of TID values representing all of the group member's TID values in the ADMIN.NME. The byte offset stored in the group's ADMIN.NME record points to the first member's record in the ADMIN.GRP which contains that user's TID value in the ADMIN.NME and the byte offset from the beginning of the ADMIN.GRP to the next member of the group. This linked list continues until a null offset (0) is encountered, which is the end of the group definition. The ADMIN.GRP contains all of the linked lists for all local global group members on the postoffice.

Each group member's TID value in the ADMIN.GRP corresponds to that member's TID value in the ADMIN.NME. Each of the local group member's mailbag numbers are then derived from the user s ADMIN.NME record that points to the user s record in the ACCESS2.GLB. The ACCESS2.GLB record contains the filename of that user's mailbag.

The external groups or users that may have been added to the postoffice address list in order to be included in the local group will have an alias type of 2. All group members that have this alias type in the ADMIN.NME will have their addresses resolved through the NETPO.GLB file. The external member's byte offset in the NETPO.GLB file will be determined from the "file pointer" field in the ADMIN.NME. The external member's record in the NETPO.GLB will then yield that member's network name, postoffice name, mailbox name, and the mailbag number for the external postoffice definition on the local postoffice. That member's mail message will then be passed to the external postoffice's mailbag where it will wait for the external MTA to send the message.

MORE INFORMATION

The following diagram may be helpful in conceptualizing the way groups are resolved.

          Byte                               TID
         Offset           TID               /---->ACCESS2.GLB --->mailbag
                                          /

                                        \
                                          \  Byte Offset
                                            \---->NETPO.GLB ----->mailbag
                                              (external users only)