Samael:Mail paramah$ ls -lah ~/Library/Mail | grep -E 'Envelope Index$' | awk {'print $5'}
54M
Samael:Mail paramah$ sqlite3 Envelope\ Index
SQLite version 3.4.0
Enter ".help" for instructions
sqlite> vacuum subjects;
sqlite> .exit
Samael:Mail paramah$ ls -lah ~/Library/Mail | grep -E 'Envelope Index$' | awk {'print $5'}
53M