What are the e-mail security problems addressed by asymmetric key encryption used in conjunction with SSL?

What will be an ideal response?

Asymmetric key encryption should be used in conjunction with SSL to provide message signatures and content encryption. This addresses the majority of e-mail security:
* Eavesdropping-All e-mail content is encrypted.
* Message modification-Message digests or digital signatures are used to prevent
modification of e-mail content.
* Message replay-A timestamp can be used with digital signature to prevent replay.
* Repudiation-The use of signatures provides proof of the sender.
* Unprotected backups-E-mail content in an SMTP server is always encrypted.