The default attachment viewer MClient.exe (C:\Windows\NOTEPAD.EXE) does not work on 64bit Windows systems
When selecting an attachment viewer in a mailbox, "this viewer" is set to C:\Windows\NOTEPAD.EXE by default.
On 64bit Windows systems this link is wrong because Notepad is located
either in C:\Windows\System32 (64bit version) or C:\Windows\SysWOW64 (32bit version).
When the path is changed manually, MClient will reset it to C:\Windows\NOTEPAD.EXE the next time it is launched.
This has been identified as a product defect under APAR IC92999