Are there any limitations to the shell-to-mailer mode ?

I am using RemoteAccess with FrontDoor:

runra.bat:
============================================
R:\RA\RA.EXE -MR:\FD\FD.EXE*M -E10 -N%1 -c%1
============================================

But it looks like RA will always exit with Errorlevel 10 (ie. "-E10").

FrontDoor has the following errorlevels:

          24.1 Errorlevels

              1       Internal error
              2       External error - missing files, paths, etc.
              3       Insufficient available disk space (less than 32 KB)
              4       (reserved)
              5       Unable to initialize modem
              6       Incorrect FOSSIL version
              7       FOSSIL not loaded or detected
              8       FrontDoor already loaded, issue EXIT to return
              9       (reserved)
              10      User break
              11-30   (reserved)
              31-255  User definable errorlevels

How do I get RA to detect those ? -- or is the only way is to use "EXEBBS.bat"
(ie. not use shell-to-mailer mode) ?
--- SBBSecho 2.99-Win32
 * Origin: Vertrauen - vert.synchro.net (1:103/705)