The security of email can be considered one of the important issues for scientific research since the nineties of the last century. This is mainly comes from the wide use of e-mail for exchanging various kinds of information especially that some of them are important or sensitive. Although there have been several solutions offered to solve this problem but we still facing the fact that most email messages sent so far have been without any security. The main reason behind this is that, the previous systems relied on the traditional public key cryptography were so complicated from usability point of view for most users.  In this work, we exploit the use of Identity-Based Cryptography (IBC) for solving this usability problem. Indeed, to further increase the system strength, IBC has been combined with mediated RSA cryptography. Our proposal includes the deployment of the two promising hybrids of mediated IBC. In both of these hybrid cryptographic systems, all operations of encryption/decryption and signature/verification have been considered. The proposed system has met the design objectives either totally or partially.  We beileve that our proposed hybrids for mediated IBC can be very helpful in simplifing the use of e-mail security so that to increase the number of users of such systems.