Add to heading subcommands

Use these subcommands to add different heading items to messages.

Item Description
~h Adds to the To:, Subject:, Cc:, and Bcc: fields.
~t addrlist Adds the user addresses in addrlist to the To: field.
~s subject Sets the Subject field to the string specified by subject.
~c addrlist Adds the user addresses in addrlist to the Cc: (carbon copy) field.
~b addrlist Adds the user addresses in addrlist to the Bcc: (blind carbon copy) field.