Hello, Thanks for all feedback I got. I am pretty sure that if I used ³openssl enc² method, it is able to handle large file over 250g size perfectly. I think openssl installed on the system is capable of doing large file support. However, when using ³openssl smime², it is not able to. Apparently it¹s smime method limitations, not the openssl. Other than smime and enc, what other methods can I use for large file support that would use the asymmetric public/private keys? - xinhuan