Here is the solution -
https://www.ibm.com/support/pages/send-function-not-working-content-manager-ondemand-windows-client-64-bit-windows-machinesThe technote is not very detailed, here are the details
The 2 registry entrees below need to be adjusted;
1. Go to HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows Messaging Subsystem
Make the following changes to the registry
Set the (DEFAULT) key to 1 instead of default
Set the MAPI key to 1 instead of 0
2. Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem
Make the following changes to the registry
Make the following changes to the registry
Set the (DEFAULT) key to 1 instead of default
Set the MAPI key to 1 instead of 0
After making those changes, the SEND button in both 32 and 64 bit CMOD clients will appear.