UNIX for Dummies Questions & Answers

Hello Experts,

When I remotely login to my Unix Box using SSH, I get the shell prompt as :

Code:

--HOST=tx2addea010 USER=nbkqu7q DIR=/home/nbkqu7q
$

There is a usergroup "transact" and to change to it I give the command:

Code:

pbrun transact ksh

to get the shell prompt as :

Code:

--HOST=tx2addea010 USER=nbkqu7q DIR=/home/nbkqu7q
$ pbrun transact ksh
/etc/profile[100]: lsuser:  not found.
[YOU HAVE NEW MAIL]
--HOST=tx2addea010 USER=transact DIR=/usr/BOFA/hosting/apps/tr3
$

In short the command being used is "pbrun" to run "ksh" and the USER then becomes "transact".
I am trying to connect to this box from my java program where I stop looking for a response from the server once "null" is received, i.e. when the box returns "null" I break from the loop and proceed with other commands.
After receiving "[YOU HAVE NEW MAIL]", the code keeps waiting for something to come which means "null" has not yet come.

questions:
1. what is exactly being returned after "[YOU HAVE NEW MAIL]", if it's not null, that keeps the code waiting?
2. Is there any other way to change to transact group except pbrun?

info:
I have tested the code for other commands, it is running fine.

Regards,
Himanshu