During the migration an error is thrown by the NMSP tool:
Migration failed with "System.OutOfMemoryException" error
NMSP application is 32 bit (because Lotus Notes does not support communication with 64 bit application). So, 32 bit .Net application has a restriction to only 2GB of memory being allocated.
There are three ways to workaround this error:
1) Run the job from NMSP Designer
2) Use “NMSPCMD.exe” tool that allows running migration jobs from the command line. It is possible to create a simple .cmd file that runs various migration jobs using even less memory.
3) Use the Quest Import Service instead of Web Services. The Quest Import Service has been designed specifically to handle large migrations with large attachments and avoid this issue.