Before:
$ proxmark3 /dev/cu.usbmodem14401
$ hf mf eload /Users/ray/Downloads/my-dump-file.eml
File /Users/ray/Downloads/my-dump-file.eml.eml not found or locked
After:
$ cd ~/Downloads
$ proxmark3 /dev/cu.usbmodem14401
$ hf mf eload my-dump-file
................................................................
Loaded 64 blocks from file: my-dump-file.eml