set dont-type-headers

SET DONT-TYPE-HEADERS [fields]  -  define header fields to be hidden

The DONT-TYPE-HEADERS variable defines one or more header fields that
  should not appear when you display messages with TYPE, READ, REVIEW
  or BROWSE.

The command LITERAL TYPE ignores this variable.

To unset it, type SET DONT-TYPE-HEADERS with nothing following.

The variable ONLY-TYPE-HEADERS overrides DONT-TYPE-HEADERS.

Example:
    MM>set dont-type-headers received, return-path, message-ID

For more help, type "help" and one of the following:
(at any prompt:)  save-init   set   show   type   set only-type-headers
                  set dont-print-headers   set only-print-headers
(at the MM> prompt:)  read   review   browse