Secure MIME (S/MIME) is used for :

A.
Encrypted and digitally sign e-mail messages.

B.
Send anonymous e-mails.

C.
Send e-mails with a return receipt.

D.
Expedite the delivery of e-mail.

Explanation:
Secure MIME (S/MIME) is a standard used for encrypting e-mail. S/MIME can also contain signature at A.
S/MIME provides encryption, integrity, and authentication when used in conjunction with PKI.
Reference: Security + (SYBEX) page 368