"ERROR: [4618-33-219-00000242] Unable to open NSF file 'C:\Domino\Data\mail\user.nsf'" (4209933)

When migrating using the File System the migration fails with following error in the error log:

ERROR: [4618-33-219-00000242] Unable to open NSF file 'C:\Domino\Data\mail\user.nsf''
NSFDbReadACL:
Special database object cannot be located

If you try to open the NSF manually the following error is sometimes displayed:
Cannot find external name: SWIFTFILEINITIALIZE

This error appears if the migration account does not have access to the NSF.

WORKAROUND

Add the Migration account to the Managers ACL on the NSF.